Do it yourself - Auto maintenance work

Nov. 13, 2017

Introduction

Once a while, I find myself in the trouble to keep up with knowledge of automobile, so I have to learn a few things through youtube.com. For example, how to install a car battery? I did once recently. This past October, how to put a backup tire, that was my favorite research through youtube.com, I got a flat tire and then I like to do some research how to fix the issue by myself.

My research is so shallow this October, I watched 2 or 3 videos to put a backup tire, and then I tried to do it myself, I could not take off lock nut off no matter how hard I tried. So I went back to watch videos, until a few hours later, one of videos shows that it is to use your feet to leverage the power. I used the tip and solved the problem puzzled me more than 2 hours.

Learning is fun

I sent my car to Canadian tire auto repair last Monday for 4 pm appointment, and I was told that the tire cannot be repaired, so two new tires will cost more than $300 dollars. I politely declined the advice, and waited last Saturday and then drove to O Tire, and I got the tire repaired. There are two nails in the tire, the cost of repair is $60 dollars, with life time warranty.

I spent 10 minutes to touch all tires's tooth in O Tire store and try to understand the technology of tire.

My low beam light

One of my weakness is to be patient and be able to solve real problem in my daily life, walk away with things like wechat talks, reading or sharing. I need to take care of a lot of things, like maintaining good friendship with Christian friends, sometimes it means a long lunch together with group of people.

I checked tonight that two of low beam light bulbs stop working. I found that low beam light has some issue, but until today in the dark outside of the home, I did make sure that light bulbs do not work.

To be outlier

It is time to review the course I learn from pluralsight.com called "Become an Outlier: Reprogramming the Developer Mind", I did in July 28, 2017. I plan to revisit the course again and try to apply the learning to my daily life.

count pairs

Nov. 12, 2017

Plan to study the hard level algorithm called count pairs, the problem statement is here.

Moving Elevator

Nov. 12, 2017

Plan to study 30 minutes a time on this hard level algorithm called Moving Elevator. The problem statement is here.

Check the leaderboard and also find a googler with code submission, the linkin profile is here.

How to convert finite automata to regular expressions?

Nov. 12, 2017

Plan to study the stackoverflow question How to convert finite automata to regular expressions?

Stock porfolio - Morgan Stanley campus codeathon 2017

Nov. 12, 2017

Introduction

It is such a great contest for me to play last weekend. I was pushing myself to get back to play coding contest and then train myself to work on hard level algorithm. The first two medium level algorithms in the contest are so helpful for me to catch up learning on C# programming and also warm up the statistics. As a software programmer, I learn that the contest does not require me to write very complicate code, I need to stay cool and also think about the foundation of statistics sometimes, need to refresh my knowledge and quickly look up.

Algorithm study 

Plan to work on the hard level algorithm called stock portfolio, Morgan Stanley campus codeathon 2017.

The problem statement is here.

It is also a hard level algorithm, my favorite algorithm to learn and apply some dynamic programming techniques.

Miss my mother and she will be remembered

Nov. 12, 2017

Introduction

It is the the first Sunday I will live without a mom in the world. She passed away on Nov. 11, 2017 at the age of 86.

My mom was such a great person who had lived her life to the full. I have so much good memory to spend time with her. Specially after I went to college, she still corrected me when I made mistakes, and she answered my phone calls when I felt lonely a lot of years, and we lived together back in Florida together back 4 months in 2000 and 5 months in 2001.

I will go to Willingdon church this morning, and I like to pray and wish everything is great with all I have.

God blesses us, have a wonderful Sunday.

Nov. 25, 2000
Julia with her mom qingfu liu in Orlando, Florida, Seaworld theme park. At that time, my mom turned 70 years old. I was in my early age to experience the life in USA.

January 26, 2012

Julia and her mom spent time at the beach of the city of Shenzhen.

Julia walked on beach with her mom in 2012. The video link is here on facebook.

2014 Chinese spring festival

Julia interviewed her mom how to celebrate China new year. Here is the link on youtube.com.

Julia took care of mom while she played tennis and had some conversation with her mom. Here is the link on youtube.com.


Oct. 13, 2017, 3 PM, first time in my life, I washed my mom's feet with the help of 3 other sisters.

Bible teaching is very good about washing each other's feet. I shared my learning with my sisters, and they all liked the idea and helped me to wash my mom's feet first time.

Quora study: Shriram Krishnamurthi

Nov. 12, 2017

Plan to study a computer professor and how he thinks in terms of education, computer science, quora platform, and other things.

The quora profile is here.

Order strings

Nov. 11, 2017

Introduction

It is the first medium algorithm in Morgan Stanley Campus Codeathon 2017. I spent a few hours to work on the code. Now it is 11:54 PM. I am trying to get more points. What should I do to get more points?

The problem statement is here.

I am very patient to read problem statement again and again, try to find the clue what is missing in my problem solving. Look at those test cases:

Follow up after the contest

Nov. 12, 2017 9:43 pm
Julia tried a few submissions. Here are the link to her C# submissions.

First submission, only score 8 out of 40. Here is the C# code of first submission.
Second submission, only score 5 out of 40. Here is the C# code of second submission. Change numeric type from int to long, score from 8 lower to 5.33
Third submission, numeric type, consider the length of string 50, check one char a time. Score goes up from 8 to 23 out of 40. 
Fourth submission, C# code is here. 

Plan to study all C# submissions.

The great game of Galia

Nov. 11, 2017

Introduction

It is the first medium algorithm of Morgan Stanley Campus Codeathon 2017. Now it is 7:38 PM, Saturday evening. I like to spend some time to work on the first medium algorithm.

I like to make this algorithm as simple as possible. Let the fun begin.

Now it is Nov. 12, 2017. It is 12:22 Am. I fully understand the problem statement, and also I like to code something for my contest.

Since the contest will end in Sunday morning 10:00 am, I am better to go to sleep and get up early at 6:00 AM to work on the contest. Now it is 12:47 AM, better to sleep on this algorithm.

Next step 

I woke up 6:30 AM, but I enjoyed the long stay on the bed with music and wechat reading. Now it is 9:32 AM. The contest will end in an hour. I need to work on something.

Read quickly on the algorithm leaf node count on binary search tree. The link is here.

These are steps:
1. Find all sequences
2. Construct binary search tree
3. Count leaf node
4. Add to the sum
5. Evaluate the algorithm time complexity and space complexity
6. Try to optimize

There is timeout issue. So I have to use dynamic programming, using combinatorics, and build a recurrence formula. So the code should be very easy.

Now it is 9:56 AM, the contest is extended to 10:30 AM.

I like to show my worksheet, and it is my way to push myself to work hard on algorithm, no matter how hard it is.

Eight years is like a blink of eye

Nov. 10, 2017

Introduction

It is like the blink of eye that I have spent almost 8 years in the city of Vancouver starting from April 18, 2010. I still remembered the conversation, plans my friend prepared for the 14 days road trip from April 1 from Florida to Vancouver, in the year of 2010.

I like to celebrate my hard working eight years!

Plan to write an answer on quora.com how I planned the trip with a friend over 14 days.

What is the third algorithm to ask code review?

Nov. 9, 2017

Introduction

It was 11:10 pm, and I spent over 30 minutes to go over the algorithm I practiced, and try to find a good one to ask code review.

Now it is 11:45 pm. The one I am reading now is leetcode 212 using trie data structure, the blog is here.

I came back from a break this September and asked two algorithms based on my mock interview practice. Today I like to find the third algorithm to ask code review.

Algorithm review

Trie 

It is also good warm up to review my favorite practice and share with the community.

Plan to study the algorithms of Trie from code review website, Trie implementation for left to right wildcard search, and another one: Trie (tree form) in Java

4 Sum

It is Harvest Time! (1 Corinthians 3: 5 - 9) (I)

Nov. 9, 2017

Introduction

It is time to review what I have completed on mock interview, I have completed almost 4 rounds of mock interview. I like to review what I learn, and show some analysis what I did good or wrong.

Let me first to give a topic for my blog, I google using keyword it is harvest time. Here is the preach I like to go over and see if I can write similar blog to document my learning. Here is the preach link, It is Harvest Time! (1 Corinthians 3: 5 - 9).

It is Harvest Time!

There are four stages to get to the harvest, prepare the soil first, sow the seed, cultivate the soil and reap the harvest.

I spend 10 - 20 minutes to go over those 28 interviews, and I read the comments for each interview. And I just enjoy the work I have completed. No matter I stumble on the algorithm or fail to help the peer, I go through the learning process.

My best teacher to help me write this series is this Moody bible institute professor, who writes very well on this article. Pastor Keith Krell is here.

Performance

This is the first time I finished over 28 mock interviews, and I remembered the worst performance to solve a Sudoku algorithm, I got rate 1 out of 7 for coding on April 11. After six month, I posted the question on code review on the algorithm on Nov. 6, 2017, here is the link called "Sudoku solver with clear structure". 

Reference

1. First round mock interviews, 27 interviews.

 

C# Array class document reading

Nov. 9, 2017

Introduction

It is best investment of time to read C# Array class documentation. What I do is to print out a copy and hold the copy to read again and again, ask questions, take notes, and write down what I learn.

Here is C# Array class, I do not have chance to go over the object-oriented design course, but I like to ask myself to memorize all APIs, and also be able to clear all the terms shown in the document.

As a programmer, I like to write code quickly using existing API of Array class, and be able to understand those interfaces as well. I find out that I am interested in the discussion on stackoverflow on those C# interface, and I try to figure out what the difference is.

Read like bible 

I like to read C# Array class like bible. I will mark those words showing in the document, and then I will use those words when I need to write blogs about the algorithm.

C# Array abstract class source code scout

Nov. 9, 2017

Introduction

It is the first time I read C# class Array's source code through Microsoft website. I spent a few hours t o read over 3000 lines of code. I call it scout since I have written a few blogs about C# Array but it is the first time I have chance to read C# code.

Take notes, please!

It is so interesting for me to read C# Array class, so I have to be able to understand why it implements five interfaces and it is an abstract class. I am very curious about how the code is structured in one class over 3000 lines of code.

Read C# Array source code here. I found the link in the first few paragraphs of Array document.

Read C# SorterObjectArray - mscor.lib, the link is here.

Plan to write down some notes to help myself to continue to get educated on C# Array, and understand the design of .NET framework. 

Leetcode 151: reverse words in a string

Nov. 9, 2017

Introduction

It is in-place to make the algorithm a classical algorithm for any language. I have practiced over a few times last 6 month, and on Nov. 8 10 PM I had chance to write the algorithm in 30 minutes, and the code passed all test cases.

Usually first few time I have to figure out the issues I have and then found ways to solve the algorithm. Last night practice is no longer challenge for me anymore, I noticed that and started to look into Leetcode 151 discussion panel after mock interview.

Algorithm study

Here is the C# practice.

Quora read: Thanh Trung Nguyen

Nov. 9, 2017

Plan to read Thanh Trung Nguyen, the profile is here.

Quora read: Lalit Kundu

Nov. 8, 2017

Plan to read the answers from Lalit Kundu, here is the quora's profile.

My favorite question is about implementation skills. The answer is here.

Leetcode 10: regular expression - Fun to play

Nov. 8, 2017

Introduction

It is really fun to play with code related to recursion tree after the mock interview. I ran into various error with a simple test case each time using Leetcode online judge, I learn from each failure and try to play with them. It is fun to play over hours and actually I like to learn something here. Let me document the issues first, and then figure out the solution later.

Test cases to help 

I like to list the test cases to help design the algorithm.

"", "a*"
"", "a*b*"
"bbbba",".*a*a"

Here is the C# code with a bug timeout - need to run at least 1 time first for a* pattern, and then run 0 time for a * pattern.


The test case for time out is here:
"aaaaaaaaaaaaab"
"a*a*a*a*a*a*a*a*a*a*c"

And the code causes the problem is shown in the following picture:

Here is the C# code with fix of timeout:

Catalan number

Nov. 8, 2017

I will write something here about the algorithm. Will come back very soon.

Transcript is here. I will write down the story later on.

Follow up 

January 17, 2018

It is the advantage of mock interview. I learned the algorithm after I had practive over a few times. But some one with very good talent on algorithm just showed me his way to solve the problem.

The peer just wrote down a 5 x 5 matrix using x to reprent each number, and then he went over the first row, to start from the first row from left to right, write down one for each column; and then go to next row, and then quickly from left to right, add the value underneath and left neighbor in the same row. He finished the process in less than 5 minutes, and then showed me the calculation of value for n = 4.

It is the best coaching experience for me. I learn that some one is much better than me to understand the algorithm. And after mock interview, the peer told me that he got some training in competitive programming before.

Leetcode 10: regular expression

Nov. 7, 2017

Introduction

It is such an adventure to work on Leetcode 10: regular expression. I chose the algorithm as my most favorite mock interview algorithm on quora.com last month, the link is here. But of course I was so nervous since I could not believe what I will write down.

My practice 

The peer was very nice and also helpful. I went over each test case and explained the matching, and I told the peer that I will use one of test cases to do whiteboard testing, recursive tree I will use at least 2 branch. For any char followed with *, I will match 0 time or 1 time or more than 1 time.

Here is my C# practice code. I ran the test cases, the code failed the test case with "" and pattern "a*". So I tried to fix it, added one base case, but still failed the test case. The code is here.

I told the peer that I will fix it after mock interview. I already took 43 minutes. Such a great workout.

Discussion between two peers 

Here is the discussion between two peers in mock interview:

how do you match "abb" with pattern "b*b"? Peer asked, and he put down the test case next to line 68.

I think that there are 3 branches in recursion tree:

b* match 0 time, so "abb" will check to match "b", return false;
b* match 1 time, so  'a' != 'b', return false;
more than 1 time will also return fail.

Let us check "bbb" with pattern "b*b", Julia suggested to work on.

We like to check 0 time, 1 time or more than 1 time.

For 0 time case, "bbb" will try to match "b" since "b*" 0 time means empty string. Return false;
For 1 time case, b matches b*, so "bb" will try to match "b", return false;
For more than 1 time case, "bb" will match "b*b", go back to 3 cases, return true.

Show some image to help understand the discussion:

Feedback from the peer

I just could not believe that the peer was a competitive programmer in high school, and then he just finished his computer science graduate school two months ago. He showed to me how strong his analysis was to handle the algorithm and coding was fast and quick later on, he finished in 12 minutes and it seemed to me that he got very good training on the algorithm. Will continue on my next blog Catalan number on the performance. The peer played contest on csacademy.com.

Follow up 

Nov. 8, 2017
The code is updated with code from line 37 to line 41 to fix the base case, empty string "" matchs "a*" pattern string.

C# code is here.

Two peers comparison

It is interesting to know that two peers can evaluate each other with top rating, but how about to compare the profile of two peers and see what we can tell from those numbers.

Divide to n small linked list with length difference at most one

Nov. 7, 2017

Introduction

It is the first time I went through a friend met in mock interview, we both worked on the same algorithm together. I wrote two version of code, one is recursive function, one is iterative one.

Problem statement can be written in the following:

Given a Linked list, split it into x number of smaller linked list where the size difference between any two list should be at most 1

Algorithm practice

It is so interesting to have discussion with the peer outside mock interview platform. I always think like a math major graduate student, the first 5 minutes I will go over anything including mathematics, and then I rested all time. Since I went through the linked list practice in 2016, here is one of linked list practice blog to document my practice. 

I like to observe how the peer picked up the analysis and worked hard on the coding. For me, it is just another routine and I do not need to think about too much. 

C# code is written here, and later on I will compile and add some test cases. 

First, I wrote a recursive solution. The link is here. And then I wrote an iterative solution, the link is here. 

Also, I like to give the code review for the peer's code. The code is here. 

Statistics

Time spent in discussion 7:15 pm - 9:18 pm 

Code review daily read

Nov. 7, 2017

Introduction


Usually there are over 40 algorithm asked in code review, but only less than 10 algorithm will be posted on twitter.com. So I just need to follow the code review twitter account and then I can follow the algorithms every day. Here is the twitter link.

On Nov. 6, 2017, there is a twitter post related to the algorithm I asked. Here is the question:
Sudoku solver recursive solution with clear structure.

Special case of Leetcode 230: Kth Smallest Element in a BST

Nov. 6, 2017

Introduction

It is the hard level algorithm called Kth smallest element in BST. When k value is one, the problem can be called to find largest smaller element in a binary search tree given the number.

It is very good discussion with the peer how to write an iterative solution. I did write down the code using C# and then I have to figure out how to get good rating from the peer.

Here is the C# practice code. I added main function after the mock interview.

Code review 

Here is the evaluation I got. I need to learn how to work with the peer, and follow the hint better.

Follow up 

Nov. 7, 2017
I found a bug in my code, the null pointer exception on line 35:
while(currentNode.right.key < num)


Here is the fix, C# code is here. currentNode.right == null is added to line 41. ( * bug fix No. 1*)

Nov. 10, 2017 11:44 PM

I finally figured out the thing I did wrong in my last mock interview. The code I wrote in Nov. 6 is wrong, and also the fix of bug on Nov. 7 ( * bug fix No. 1*) is also wrong. I finally understood that I was too stubborn and did not take the advice in mock interview.


Also the above code will not work for the following binary search tree:

Given the value 11, largest smaller BST key's value should be 10, but the solution will return 8 instead. Also the above code has null pointer run time exception on line 36, currentNode's right child may be null pointer, need to put a guard clause to check currentNode.right != null.


Nov. 10, 2017
11:19 PM
I had 10:00 pm mock interview, the peer worked on the algorithm. I had chance to find my problem based on the following test case. Great thanks for the peer, who is very patient, and think about the test case carefully.

Given number 11, the largest smaller BST key is 10. How to find node with value 10?   

First, start from root node with value 19, 19 is bigger than 10, so go to its left child. Left child value is 8 and it is smaller than 11, then set the value to look for (denote as LargestValue) as 8. And go to its right child to search. The node's value is 11 which is not smaller than 11, then go to left child 10, and set LargestValue = 10. Node 10 is leaf node without any child. 10 is the answer. 

In other words, find smaller one, go right; find bigger one, then go left. Until the traverse reaches the leaf node. Left, right, left. 

Learning Interface through C# 2000 things

Nov. 6, 2017

Introduction

I got some advice to code to interface through the code review, so I plan to spend 2 hours to go over all interface things through C# 2000 things.

Here is the snapshot:

Code to Interface

It is so interesting to know that I enjoy to go over interface learning through C# 2000 things first. In order to understand the C# array and also IEnumerable interface, I need to go over the basics of C# first.

Actionable Items

Study Abstract class Array

Nov. 7, 2017


Actionable Item

Work on C# Array abstract class study

How many interfaces are derived from?

IClonable
IList
ICollection
IEnumerable
IStructuralComparable
IStructuralEquatable


Properties


IsFixedSize
IsReadOnly
IsSynchronize
Length
LongLength
Rank
SyncRoot

Method ( 10 methods a time)

AsReadOnly<T> (T[])
BinarySearch(Array, Int32, Int32, Object)  Use IComparable interface implemented by each element of the array and by the specified value.
BinarySearch(Array, Int32, Int32, Object, IComparer) Search a range of elements in a one-dimensional sorted array for a value, using the specified IComparer interface.
BinarySearch<T> (T[], T)
BinarySearch<T>(T[], T, IComparer<T>) Searches an entire one-dimensional sorted array for a value using the specified IComparer<T> generic interface.

BinarySearch<T>(T[], Int32, Int32, T) Searches a range of elements in a one-dimensional sorted array for a value, using the IComparable<T> generic interface implemented by each element of the Array and by the specified value.

BinarySearch<T>(T[], Int32, Int32, T, IComparer<T>) Searches a range of elements in a one-dimensional sorted array for a value, using the specified IComparer<T> generic interface.

Clear(Array, Int32, Int32) Sets a range of elements in an array to the default value of each element type.

Clone()
ConstrainedCopy(Array, Int32, Array, Int32, Int32) Copies a range of elements from an Array starting at the specified source index and pastes them to another Array starting at the specified destination index. Guarantees that all changes are undone if the copy does not succeed completely.

Start to read a question:
Why array implements IList?

IEnumerable vs IList

Nov. 8, 2017

What problem does IStructuralEquatable and IStructuralComparable solve?

Nov. 9, 2017
Read C# Array source code here. I found the link in the first few paragraphs of Array document.

Read C# SorterObjectArray - mscor.lib, the link is here. 

Code Review: Sudoku solver recursive solution with clear structure

Nov. 6, 2017

Introduction

It only takes less than one hour to post the question on code review. The algorithm is Leetcode 37: Sudoku solver, the most classical depth first search algorithm. My practice is documented here.

It is a wise decision to ask a question on code review website, this time I learn a few things from code review.

Code Review

Code review link is here.

I got very good review. My most favorite advice is Code to interface. Use IEnumrable<char> instead of using HashSet<char>.

Shen Neil - Shanghai Jiaotong university alumni

Nov. 5, 2017

Introduction

It is so interesting to be an alumni of Shanghai Jiaotong University, China. I went back to have a vacation this October, I had to meet classmates of undergraduate 70141 and also graduate class 8902.

My undergraduate class is named as 70141, and my graduate class is names as 8902.  I had chance to meet some of my classmates and I had chance to follow more on wechat about their stories. One of 8902 classmate posted the blog about Shen Neil who is my undergraduate classmate of 70141, of course, he is no longer the first degree of my friend circle. My close friend's circle is engineers and teachers of alumni of 70141 and 8902 classes.

Here is the article written in Chinese for me to study in 20 minutes tonight. Chinese sentences are written like this: Four year Shen Neil makes 2 billion dollars, but he invested 50 billion first, in 11 years make 2600 billion dollars.

" 投资教父"沈南鹏，4年赚到20亿还嫌不过瘾，他一举砸下500亿 , 11年创下2.6万亿奇迹!

Study of Shen Neil 

Shen Neil's wiki page is here. 

Shen Neil's wiki page in Chinese is here. 

His partner of Sequoia: Michael Moritz

52 minutes interview called Sequoia's Neil Shen to Entrepreneurs: "Follow Your Heart", the video link is here published by Stanford Graduate School of Business.

Several arguments to look into from the article:

Arguments:

不过天才就是天才，在十几次面试的过程中，沈南鹏就摸到了门道。

此后不到两个星期，他就把江恩理论、5个波浪循环、MBS、CDO、中国国债、布伦特原油报价等问题搞透了。

Facts:

就在另外两个人绞尽脑汁在纸上比划的时候，沈南鹏不到5分钟已经给出了答案。

原来不太懂中国的商业环境，到了1999年，我已经比较‘土鳖’了

Leetcode 611: Valid Triangle Number

Nov. 4, 2017

Introduction

It is the medium level algorithm. The algorithm is very challenging to lower the time complexity from O(n³) to O(n²) using two pointer techniques or binary search. The peer gave me the hint to lower the time complexity, and then I started to think about binary search with time complexity O(n²logn), and then the peer gave me hint to continue to optimize the time complexity.

Plan to write C# code and also read discussions for the algorithm in short future.

TED Talks: 'Grit: The power of passion and perseverance'

Nov. 4, 2017

Watch 6 minutes video, a TED talk: Grit: The power of passion and perseverance. The article with video link is here.

Plan and budget

Nov. 4, 2017

Introduction

I like to write something about project management and cost analysis, and share my story about my October vacation.

I came back from the vacation on Oct. 20, 2017, recovered from the jet lag, and started to catch up the projects at  work. And I like to document how I learn to plan and how to budget, and understand how I can make things better.

It is time to talk about money, and I believe that a very smart programmer should have learned so many things through years, and I just make you laugh when I share my learning and how I understand the money talk.

Money talk 

Will come back very soon.

Galaxy S6 - Tips, Tricks & Hidden Features

Nov. 4, 2017

Introduction

It is two months to be a user of Samsung Galaxy S6 mobile phone. I enjoy so many things last two months and really like to write an eulogy for my new companion - a refurbished Samsung S6 phone.

As a mobile phone user, I need to keep learning the mobile apps and keep update specially weekends.

Study of the video 

I always said those sentences in my vacation to my sisters, "I do not need a brand new iPhone or latest version Huawei phone,  or a brand new luxury car to help my confidence. I am a consumer and then I tell you what I like to use, a used one."

My point is that it is not too difficult to purchase a brand new phone, I can spend extra $200 or more to get a brand new Samsung S6 this August. It takes so much time to catch up the advanced features for the phone. As a website developer, I also have to educate myself as a product manager for the website, I need to learn how others are expecting to use the mobile phone first, and then estimate how much computing power I can generate and produce a decent mobile website.

12 minutes video is here called Galaxy S6 - tips, tricks & hidden features.

17 minutes video is here called 10 Hidden Features of the Samsung Galaxy S6 You Don't Know About.

Actionable Items

Follow up
Oct. 13, 2019
I found out that I did not learn the basics of investment. I found out that in 2018 I had over $50,000 Canadian dollars with Scotia bank, I earned less than $10.00 dollar interest in 2018.

I also reviewed my US dollar account with Scotia bank from 2010 to 2017, but I did not have any interest. I found out that I wasted so much opportunity, since I missed 10 year bull market from 2010 to 2018.

Leetcode 41: First missing positive (II)

Nov. 4, 2017

Introduction

It is so pleasant to meet a peer through mock interview, and watch and learn how the peer solves the algorithm with a few of hints, write optimal solution to pass all test cases. Through 40 minutes interview, I also had chance to review the code, shared my experience of coding style, how to apply to the peer's code.

It is so exciting to see how I can learn to share my experience just in-time, and help a young programmer to pay attention to coding style. One thing I liked most in mock interview is to show the peer how to break giant expression, what to iterate in the while loop.

Also the peer chose to use C programming language, so I know that she must be a top-talented person, because those machine learning algorithm matches me to top talent in the world this Saturday morning. Only few of us can choose to use C to do interview these days. Through mock interview, I experienced C programming and do not pay attention too much since I need to refresh my C programming knowledge.

Algorithm Talk 

Leetcode 18: 4 Sum

Nov. 4, 2017

Introduction

It is such a great mock interview this morning starting from 10:00 am. I had to work on the algorithm Leetcode 18: 4 sum in the time limit of 35 minutes. I did a few things to make the mock interview great learning experience. I wrote an algorithm, passed the compiling and then passed all test cases without any bug. The algorithm has optimal time complexity although extra space is needed.

Here are highlights:

 1. I chose the algorithm using time complexity O(n²). Two sum pairs are saved to the dictionary for lookup later on.

 2. Whiteboard testing was very helpful, I chose the easy one [3, 2, 1, 4, 5] and the given 4 sum is 12 = 1 + 2 + 4 + 5. Compared to the test case given in the problem statement, this one is easy to follow.

3. Through whiteboard testing, I found a bug in my design. The array may have duplicate numbers, and then I spent extra 5 minutes to change the design, in line 78, I added two extra elements in the array to save index number of the array.
newList.Add(new int[]{no1, no2, i, j})

4. Through the whiteboard testing, I modified the code to make it more easy to follow. I added var no1, no2, no3, no4, assuming that no1 <= no2 <= no3 <= no4, and the index of four numbers in sorted array is in ascending order.

5. I spent less than 3 minutes to fix all compiling errors.

6. The code runs and pass all test cases without any bug.

Code review

The code I wrote in mock interivew in C# is here to view.

Based on my last practice on Leetcode 18: 4 sum in August 2017, I worked on the feedback. I need to write a run-through code, I have to simplify the solution in order to fit in 30 - 35 minutes.

A few things I did are very helpful to expedite the process this time. The most simple test case is chosen to do whiteboard testing; the whiteboard testing is not a fake one, in the process of testing, I found a bug first, and then came out the fix, and in-between I added a few more variables to make code more easy to follow, avoid bugs.

Feedback from the peer

The peer did not choose to use the video, but her knowledge of algorithm is very helpful. I did have chance to learn the algorithm compared to two pointers techniques.

Leetcode 37: Sudoku solver

Nov. 2, 2017

Introduction

It is the time again to write a Sudoku solver. Here is my C# practice, the peer told me that I do not need to run the code using web browser compiler.

The mock interview was supposed to end in one hour to 11:00 PM, but it actually ended at 11:50 PM. I spent more time to chat with the peer until the session terminated due to timeout.

After that, I started to run the code, first I fixed the grammar error line 62. The Split function of string will have an array of string, not an array of char. The line 62 has compile error. It is the easy and quick fix. But I came cross the index out of range run time error. This one I could not pinpoint the error.

I was troubled and tried to set up test case until 1:00 AM, and then I called it a day. I did not do whiteboard testing, instead I tried to guess what is possible places to go wrong for index-out-of range error. With whiteboard testing, it should be a quick fix. But without it, I wasted almost one hour but I still could not find the issue until 1:00 AM.

Whiteboard testing

The whiteboard testing is to use a test case and go over the code line by line, write down the value for each variable, and run the code virtually with results.

If I do whiteboard testing, I should have found the bug on line 91. Here is line 91 with the bug:

for(int row = startRow; row < row + 3; row++)

actually when I run the whiteboard testing, startRow = 0, then row is from 0 to 2. The statement should be written in the following:

for(int row = startRow; row < startRow + 3; row++)

Nothing beats whiteboard testing 

In terms of bug fixing, nothing beats whiteboard testing. Go over a simple test case, go over each line of code, put the result next to the code.

Actionable Item

C# code is updated and it passes all test cases after mock interview. The C# code is here. 

Review sudoku algorithm on code review website, and I studied the question:

Solving Sudoku using backtracking

Plan to write C# code based on the above code review. I feel that there are a few things I can apply to my mock practice code. 

Plan to write a blog to review algorithm of longest common subsequence written in Chinese. The link is here.

Leetcode 41: First missing positive

Nov. 1, 2017

Plan to look into Leetcode and find the similar algorithm called get smallest nonnegative number.

Get smallest nonnegative number, do not change the array.

My C# practice code is here on Nov. 1, 2017

Also, I spent almost 50 minutes to interview the peer on Nov. 2, 2017 and had some discussion about the algorithm. I like the peer to go over the base cases to show very good reasoning.

[],   0
[0], 1
[1], 0
[0, 2, 3]  1
[3, 0 , 2] 1
[0, 1, 2, 10000]

Leetcode 41: First missing positive 

It is the hard level algorithm. Time complexity is O(n), space is O(1).

Quora reading time: Drew Eckhardt

Nov. 2, 2017

Plan to read more on quora.com, the user Drew Eckhardt's profile is here.

Role model on hackerrank

Nov. 1, 2017

Introduction

It is a small world these days, I know that every 6 people can get you connect to any one in the world assuming that you only reach out the person you know.

Today I went over the leadboard of hackerrank woman codesprint, and then I saw one of players and was so amazed about the player's hard work.

The player completed more than 100 algorithm practice on project Euler less than one month.

Leetcode: binary search tree inorder successor

Nov. 1, 2017

Introduction

It took the peer 60 minutes to write a solution to find binary search tree inorder successor on Oct. 31, 2017.  One time the peer asked me who I am, are you a teacher?  I must be very patient and be very supportive.

In fact, I understood that I failed at least 30% of algorithm in the first round of mock interview starting this March. So it is very easy for me to relate to my performance, I am in trouble, and have some difficult time to solve the algorithm.

Algorithm study

Plan to study the binary search tree inorder successor algorithm. Read as many discussion as possible, here is the Leetcode discussion link.

Common bugs for wrong answer

Oct. 31, 2017

Introduction

It is so time consuming to find the bug in my code, and then after almost over 5 minutes, I decided to use Console.WriteLine to help, because I gave up whiteboard testing. The peer insisted that the test case of platform is working, and then I found out that I should add a statement to break the for loop.

Code review 

Here is my C# code.

I spent over 5 minutes to do whiteboard testing, but I could not find the bug. The line 38 break statement is missing. Need to break the for loop.

Actionable Item

Need to work on whiteboard testing. If the result is wrong, then I need to figure out the reason without using debug statement.

Plan to do some research about wrong answer bugs.

The feedback is that "only test 2-3 times".

Play by play: html, css, and JavaScript with Lea Verou

Oct. 31, 2017

Introduction

It is the time to catch up some learning of JavaScript through pluralsight.com. I chose to study the course today, I spent one hour to go over the course, here is Lea Verou wiki page.

First I spent around 2 hours to study code review of JavaScript, the learning of JavaScript was kind of slow and not efficient, so I decided to choose an advanced course to study through pluralsight.com. I chose the course Play by play: html, css, and JavaScript with Lea Verou.

Course Study

Book To Read

CSS Secrets

Nov. 1, 2017
Continue to watch the video, HTML Game View
Accessibility and Styling.

2017 year end JavaScript code review

Oct. 31, 2017

Introduction 

It is the time to review what I have completed in 2017. I like to go over JavaScript and see if I can boost my JavaScript skills in the last two months of year. I chose to study 2 hours code review conducted by BlindMan67.

Code review 

Leetcode 238: Product of Array Except Self

Oct. 29, 2017

Introduction

It is over 30 minutes to write the algorithm based on the idea using dynamic programming. By going through the whiteboard testing, it took me two steps to come out the code passing all testing cases. First I wrote code to make sure that the value was correct, and then I change the code based on TED principle.

Code study

C# code is here.

I wrote two blogs about the algorithm, the first one is written in March 21, 2016. . The second one is here written in July 24, 2015.

Women's codeSprint 4: Afraid of the dark - after the contest

Oct. 29, 2017

Introduction

It is time to study the algorithm after the contest. I like to study the editorial note for the algorithm - afraid of the dark. It is an algorithm using BFS, DFS, union-find, greedy algorithm. Time complexity can be O(n).

I felt that I have to start all over again, I could not perform the contest in less than 10 hours, I have to dedicate long hours in order to perform in the contest. How can I dedicate so many hours for a contest? How can I motivate myself to stay focus on problem solving?

The problem I have is that I solve more complicated problem than I should. Based on past experience on contest, the solution should be very simple and no complicated code for the contest, specially for medium level algorithm.

Actionable Item

It is a good idea to take 30 minutes at least every day to go over all the algorithms in Women codesprint #4, spend time to write code for each algorithm.

Plan to write C# code for the algorithm.

Woman codesprint 4: Extra Sweet - after contest

Oct. 29, 2017

Introduction

It is time to look into the answer of extra sweet. I started to review editorial notes, look into the leaderboard, and also study test cases. I found the code to study, here is the Java code.

Code study 

As a programmer, it is very important to be able to understand the algorithm in small detail. For some reason, I miss the important clue to solve the problem.

I spent time to look into the code and then finally I understood the idea by studying one of Java submission. Here is the Java code.

Starting from 7:10 am, now it is 8:20 pm, I never had such great time to study those code submissions and concentrated the problem solving.

Here is the design to study through the above Java code:

In the contest, I tried to set up the double linked list, and I like to set up 0's next points to 6, and 6's previous link to 0. Compared to the study code, no array is need. Just set up a map to add 1 as key, 6 as value, and then 5 as key and 0 as its value.

Women's codesprint 4: Afraid of the Dark

Oct. 28, 2017

Introduction

Now it is 11:19 PM, only 10 hours left for the contest. I only score 19 points, I need to start to work on second medium algorithm called Afraid of the Dark.

It is too late to write code for the algorithm. Now it is 1:51 am. I reviewed the graph algorithm through my coding blog, one popular algorithm is called union find algorithm.

It is not difficult to figure out the solution. We can form the disjoint sets, and then each node belongs to one of set. For set with even number of off light bulbs, the number of visited node is the size of disjoint set. For set with odd number of off light bulbs, each room with off light bulb will have a minimum distance to the leaf node.

Algorithm coding

Plan to write code after the contest.

Actionable Item

It is time for me to review my practice. I felt less engaged to the hackerrank contest, I prefer to read some material on quora.com, but I will be better off to write code and try to push myself to solve algorithm problems.

I do not need to consume so many question/ answers on quora.com. Please limit time to read on quora.com as well.

Women's CodeSprint 4: Extra Sweet

Oct. 28, 2017

Introduction

It is time to work on the algorithm called "Extra Sweet". I tried to enjoy the problem solving but after a few hours I only scored 4 out of 30 points on this medium algorithm.

Progress report 

Now it is 11:11 PM, Oct. 28, 2017. I need to move on next medium algorithm.

Follow up 

Oct. 29, 2017  8:26 PM
After the contest, I did study editorial notes, and also go over some code submissions.

Here is the code I wrote in the contest, I tried to set up linked list to double link two nodes.

Nov. 1, 2017
It is hard to figure out what was wrong with my research in the contest. I did try to figure out the issue, I made 4 submissions.

Extra sweet

First submission - the issue found and then I started to work on, mix the setup of linkedlist with the calculation of extra sweet.

Second submission - set node's left neighbor to the first node with value 0.

Third submission - set line 89 - point to the next point to the dummy node nodes[n] with index value 0.

Quora study: Dmitriv Genzel

Oct. 28, 2017

Introduction

It is the interesting place to see people write so careful and with so much detail on quora.com. Usually I like to read on linkedin.com, but now it seems to me that quora.com is better place to read.

Dimitriv Genzel is the machine learning team lead of quora.com. I like to study one of his post recently. The link is here. His profile is here.


Read one more answer from quora product manager, here is the link.

Read one answer about using competitive questions to prepare for facebook interview, the link is here.

China open quarterfinal Dimitrov

Oct. 28, 2018

Introduction

I spent over a few hours to watch live China open quarter final Dimitrov against Spanish player. It is the first day of my vacation in China, October 6. I could not believe that the experience was such great one, I like to write down some notes and continue to do some research about the player.


The coach team was sit next to me in less than 2 meters, I kept hearing the coaches were calling, "Find ways", "Are you sure". This was the first time I observed how coaches involved the match actively.

I knew the coach crew by watching one of practice video of Dimitrov before. Here is the link called Pushing the limits with dimitrov part one, 5 minutes video. Here is the link of part II, 2 minutes video.

Air canada shanghai to vancouver flight

Oct. 28, 2017

Introduction

It is such a pleasant flight that I like to write a short eulogy for the trip. I traveled with Air Canada Oct. 20 from Shanghai to Vancouver.

Find the smallest substring that contains some given subset of characters

Oct. 28, 2017

Introduction

It is a long journey for me to come out the solution to pass all test cases. I did at least 4 or 5 time last 6 months to work on the algorithm called "Find the smallest substring that contains some given subset of characters". I posted the question on code review, link is here in Sept. 2017.

Today I had chance to interview a peer using the algorithm, I only can hear the voice no video, but I understood how tough the algorithm can be, specially for the first time player. The peer does not work on the algorithm before, and I worked with him near 50 minutes on the algorithm. First 20 - 30 minutes to work on the algorithm itself, I had chance to follow what he approached the problem. Next 20 minutes I asked him to write code so I can evaluate his coding skills and coding style.

The mock interview is such a nice place to meet people and figure out together how to improve technical skills. The conversation is interesting and also very gentle on the topics. I have to let the peer approaches the problem first, and then give some hint, and see how discussion can continue.

The peer is very diplomatic so I know that he must be an important role in his job. First he chose to use JavaScript to code the program, so I complimented him about he must know node.js framework.
Then I noticed that he wrote down some notes to show his logic thinking, it is very clear; he asked my feedback so I know that he is also very good listener.

Mock interview 

I found out that I always get best peer in the world, so I have to keep up with the peer about technical skills, help them to understand their strength and weakness. It is so interesting to have a mock interview.

The test cases discussed in mock interview are the following:
1. yxxz -> "yxxz"
1. xxyz ->"xxyz"-> "xyz"
2. slide window, two pointer technique
left pointer and right pointer
3. Move right pointer first, and then find a substring; and then move left pointer to make the substring smaller if possible.

For analysis, if the peer can come out the test case like the following: For example, for search string ['a','b','c'], source string "aefbcgaxy", the shortest string is "bcga", the peer has excellent analysis of algorithm, assuming that the peer does not work on the algorithm before. 

Julia's practice 

It is also a great idea to review my practices:
April 2015, blog is here.
April, 2017, it is documented here.
June 29, 2017, mock practice C# code is here.
Sept., 2017, it is documented here.
Code review is here.

Oct. 31, 2017
It took me three years to fully understand the algorithm and how to work out a perfect solution. This experience taught me how to treat others, more patient please. And this is the really great algorithm to evaluate the candidate the algorithm analysis and technical strength.

Code review "LINQ and string.Split do it yourself practice" (II)

Oct. 27, 2017

Introduction

It is the first time I understand that the technical strength can only be trained by dedicated practice. Today I had chance to walk through those five lines of C# code, and explained to the peer how to apply those things in C++ code.

Will come back to document more about the experience as an interviewer. My last blog about the code review is here less than one month ago.

Algorithm talk 

The peer likes to write C++ but the complexity of code is beyond his expectation. 30 minutes is too short to come out the workable solution.

Here is the C# code written by code review on stackexchange.com:


Each step in the above C# code can be a small function written in C++ if the peer does not know the regular expression, or similar LINQ method. 3 or 4 years job experience does not help to train yourself to be a good C++ programmer. You need to train carefully.

Actionable Item

Plan to do some research about post vacation syndrome. I need to get out of relationships from the family back in China, less frequent using wechat to communicate family in China anymore, and get back to my normal work day in the city of Vancouver. One thing I choose to do after I overcome jet lag is to practice mock interview every day 10:00 PM. Need to meet new people and learn more about the industry and people.

Give myself a pat on my shoulder. Show my report of first mock interview after a month break.

Whiteboard testing is the savior

Oct. 26, 2017

Introduction

It is the best decision to practice mock interview starting from today. As usual, I choose to practice 10:00 PM since it is too late to work and usually I am so tired, usually I have difficult time to think clearly after long day, I like to drill myself to simulate tough situation at work. My last practice is Sept. 27, 2017. Since I took a vacation from Oct. 5 to Oct. 20, I did not practice mock interview at all.

Today I spent first 15 minutes to write code, and then I relied on my techniques using Terse, Express the intent, Do one thing (TED) principle, and then I made the change to look ahead to determine if it is ready to compare (line 33: readyToCompare), I passed all test cases in the 35th minute.

In summary, the algorithm I had to write is a linear scan algorithm, instead of looking ahead to determine if it is the last row in the current time stamp, first 25 minutes I worked on the idea to look backward to compare to previous time. Once I play with whiteboard testing, I figure out the solution 100% correctly.

Code review

C# code is here. Plan to highlight a few changes I made.

Line 29 - comment out line 29, the peer reminded me no need to use startNewTime, previousTimeStamp

Line 40 - max = sum;  // the peer reminded me that sum is the new max value.

Actionable Item

Usually linear scan algorithm I should aim at 10 minutes to perform.