Leetcode algorithm

June 4, 2018

Introduction

I got the list to work on from my coach. I like to work on the algorithm.

Hi Jianmin,

I just took a look at those problems on leetcode. Here I recommend some problems you should take a look.

https://leetcode.com/problems/3sum/description/

https://leetcode.com/problems/merge-k-sorted-lists/description/

https://leetcode.com/problems/validate-binary-search-tree/

https://leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/description/

https://leetcode.com/problems/word-break/description/

https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/description/

https://leetcode.com/problems/kth-largest-element-in-an-array/description/

https://leetcode.com/problems/132-pattern/

https://leetcode.com/problems/lru-cache/

https://leetcode.com/problems/simplify-path/description/

Best wishes!

Say goodbye to my coach

June 4, 2018

Introduction

It is hard for me to work on algorithm back to alone, and try to find another best algorithm player along the mock interview practice. I did find very good friend to practice with through blogging. I could not believe that power of marketing of each blog, I can easily get all the important information at my finger, and find a strong algorithm player to bounce ideas and work together to reach a new target.

Say goodbye!

I did write an email to say goodbye to my coach.

hi, 

  I wrote a blog to put all coaching session together, and like to share with you. 

  Here is the blog link.

  I also spent a lot of time to think about the coach I like and guess what you look like, my favorite tennis player Dimitrov's coach. I wrote blogs to share with you, but I was too busy to send too many emails. 

  Here is the coach's advice. 

 "Trust your instinct. You already practice all patterns. Figure out ways to solve the problem, make mistake and let it go." The coach talked about how to mentor the player mentally. I think that you are kind of the style, on dynamic programming solution coaching. 

  Here is blog I wrote to send to you. 

  One more coach I like and I thought about is Rob Kentlay. 

  The coach is my favorite.   

  Daniel is my favorite coach, and you must look like him. 

Leetcode 85: Maximal Rectangle - from my coach

June 4, 2018

Introduction

I talked to my coach that I had some difficulty to come out dynamic programming solution idea in the first five minutes on my last practice with the peer. My coach told me to check algorithm Leetcode 85: Maximal Rectangle.

careless whisper

June 4, 2018

Introduction

I had mock interview this morning with my coach, 8:00 AM. This is our goodbye meeting. I talked to my coach that the dynamic programming solution is hard to come out in the first five minutes. I just named this algorithm as careless whisper. I did hear the word coming out my mouth when I discussed with the peer yesterday, using dynamic programming.

Algorithm is called to find maximum flower. Given a matrix with cells three options: empty, wall, flower, find maximum flowers cell.

Let us say that two dimension grid contains empty cell (S) or flower (F) or wall (W). A person standing in a cell can see north, south, east and west. But all flowers behind wall are invisible. Find the cell with maximum visibility.

S   F   S  F
W S   F  S
F  W  S  F
S  F   F  W
S  F   W S

output: 3

Algorithm practice

Here is my C# algorithm.

I do not have time to put those four functions into one function, avoid code duplication. 

Follow up

June 20, 2018

The friend just shared with me the discussion panel on this algorithm. 

Discussion of maximum visible is here. 

Follow up 

March 5, 2019

I asked the algorithm in mock interview on interviewing.io. I learned from the interviewee that the algorithm can be simplified by checking left/ upper two directions only.



March 6, 2019

I spent time to work on the example again. It cannot be simplified. 

Leetcode 493: Reverse pairs

June 3, 2018

Introduction

It is hard level algorithm called Reverse pairs. My peer asked me to solve the algorithm.

Mock interview

Here is the transcript.

Booking reading: Microservices from design to deployment NGINX

June 3, 2018

Introduction

I like to read the book 30 minutes a time in next few days. Here is the book titled "Microservices from design to deployment NGINX".

Count how many palindromic substring - from my coach

June 3, 2018

Introduction

It is my ninth mock interview with my coach. He gave me the dynamic programming solution to work on. It can be described "Given a string, you task is to count how many palindromic substring in this string."

I tried to get help from my coach, I like to see how he developed the solution using dynamic programming. Actually I found out that I missed the target.

Target

What is time complexity to solve the problem. The brute force solution will take time complexity O(n^3). The algorithm can be solved using dynamic programming with time complexity O(n^2).

All we have to do is to get dp[i, j] for any i, j from 0 to n where n is the length of string.

And then I can use O(n^2) to calculate the count of palindromic substring using O(n^2).

Flatten a list - from my coach

June 3, 2018

Introduction

It is the algorithm my coach gave to me on mock interview June 1, 8:00 AM. I like the conversation we had and then I had some conversation with the coach. My idea is that there are so many ways to solve the problem.

After I solved the algorithm, the coach asked me to write the solution of preorder traversal of tree using iterative solution. And then he told me that the solution to write iterative way for flatten a list is the same idea.

The coach helped me to clear up the confusion of preorder traversal. The order is always defined from the root node's position.

Mock interview 

Here is mock interview transcript.

Here is the code I wrote for preorder traversal iterative solution.

Follow up 

June 3, 2018

Ownership story II

June 3, 2018

Introduction

It is ownership leadership principle. I learn the lesson how to be owners.

I need to write two stories today.

Story II

Ownership

----------------------------------

Situation:

I do not have people to work with in terms of software developer. I am the only developer.

I am too busy to work on so many projects. I do not know what is most important in the long run. 

Task

I need to find ways to improve my soft skills, and also write code every day.

Action

I worked on the same 30 algorithms last 12 months with 300 mock interviews on mock interview platform.

Here is detail:

https://github.com/jianminchen/Mock-interviews

I spent one hour to work on algorithms every day; and I followed up more coding and study after each mock interview. 

Result

I learn so many things through various peers. After each mock interview, I push myself to write code for one algorithm. I have done this 300 times. That makes me a super powerful programmer. 

I never have favorite algorithms. Now I have 30 algorithms. I learn to master all of them, even hard level ones. 

Ownership story I

June 3, 2018

Introduction

It is hard for me to learn leadership alone. I had a conversation with my friend, he kept telling me to follow S.T.A.R structure. I like to write two stories and share with him. Now it is 12:15 AM. I just finished the story.

Ownership

Leaders are owners.

Ownership

----------------------------------

Situation:

No one gives me technical code review at work

Task

I need to improve my code quality

Action

I asked 40 questions on code review stackexchange.com from Nov. 2016 to Now

Result

I found out that I need to work on C#, clean code, coding style, OO design applied in C#; after last 12 months to work on feedback, I can write much better code

Here is the story one. 

What I wish I had know before scaling Uber to 1000 services

June 2, 2018

Plan to watch 40 minutes video. The link is here.

What is microservice architecture?

June 2, 2018

Introduction

It is my research topic today "What is microservice architecture?". I had a coach to coach me one hour how to understand Netflix microservice video and pdf file, and then I like to print out something and make sure that I can understand basic terms.

Microservice architecture

I like to print out this article and read the article. At least I ask three questions and see if I can learn from the reading.

It is hard to quickly understand a new way to do software and I have to learn from the person who has strong industry experience.

Here is the article.

Netflix's Viewing Data - System design study

June 2, 2018

Introduction

I plan to spend 20 - 30 minutes to read the article and then I like to have some discussion with my coach about this article and learn how to understand system design article.

Taking notes first

Being a good student, I need to learn how to read the article carefully. Take some notes first. I like to do something small, and also start from there.

Here is the article link.

Netflix Microservices Talk

Please watch the video 48 minutes called Microservices at Netflix Scale: Principles, Tradeoffs & Lessons learned. R. Meshenberg

Pdf link is here.

Scaling time series data storage - one hour coaching

June 1, 2018

Introduction

It is my idea to get help from my Canadian coach to help me understand the article called "Scaling time series data storage". We spent one hour together to go over the article, I asked a few questions. Since I found out that there are too many new concepts in the article, I need some coaching from the friend.

System design

I like to write down some notes about this one hour coaching. First time I have luxury to enjoy best coach in the world, who helps me to understand the article word by word.

The coach told me that he spent at least half year to understand Cassadra and related technology.

Personality challenge

May 31, 2018

Introduction

I like to talk about software programmer personality as today's short research topic. I met a friend Tony today on tennis court, he knew me over 8 years. We talked about how he trained his daughter to be a professional tennis player. She is 14 years old.

My personality

I was given a lesson how to be a coach. Give room to the person. Let her grow and then figure out things by herself. Do not overdo.

I like to confess that I was too shy to make a mistake 8 years, one year ago.  I definitely improve a lot after I play hundreds of hours tennis. I learn from tennis sports.

I definitely get better after I had conversation with tennis coach.

Tennis workout

May 31, 2018

Introduction

It is time for me to go to tennis court and enjoy outdoor sports. I went out and had a good time on tennis court. I need to relax myself and work on some sports training.

My friend showed me how good his daughter is on tennis. His daughter is champion of 2018 ROGERS JUNIOR OUTDOOR NATIONAL CHAMPIONSHIPS. He showed me the website with her ranking point 9.

How to train a tennis player professional?

We chatted more about how to train the kid from age 5 to age 14, and how to train her to be a professional player.

I have known the tennis dad over 8 years. I saw how dad trains his daughter since she was less than 7 years old.

Sleepless in Bejing and early bird in Vancouver

May 31, 2018

Introduction

How can two people meet with such busy work and life? A young graduate will sacrifice sleep and meet 11:00 PM to 1:00 AM in Beijing, and an early bird in Vancouver will get up before 7:30 AM and prepare to be coached for three weeks drill. I think that the blog should definitely be called "Sleepless in Beijng and helps early bird in Vancouver".

It is such great experience to have a series of mock interviews from May 12 to May 31, 2018. We have met over 8 times in total connecting from Beijing to Vancouver. I could not believe that it is such an enjoyable thing to do. I will write down a few things I learn through the series of mock interviews.

Good partnership

I know that a good coach will work with different players. I enjoy the time to work with my coach. I start to know his personality and also very good hard working stories now. My coach is cool as the youngest tennis coach Daniel Vallverdu  who coaches ten 10 ATP player Dimitrov.

I always follow tennis professional players, one of favorites, Safarova, and think about getting a coach like Rob Steckley. My research topic is similar to surviving after 30. One practice I am done!

First blog:

Introduction to get help from a coach is written in a blog called special three weeks drill.

836 minutes working together

It is definitely a big number, 836 minutes, close to 14 hours. There are eight mock interviews in total up to May 29, 2018.


First interview ( 71 minutes)

Detail see my blog called first mock interview from my coach.


Second interview (108 minutes)

Minimum cost using dynamic programming - mock interview

The transcript is here written in mock interview. And the code is written after the contest.

Find least number of perfect square, the blog is here.



Third interview (101 minutes)

Next large element in the array, the blog is here.

Height of tree, the blog is here.


Fourth interview (114 minutes)

The mock interview is documented here. The algorithm is called ....


Fifth interview (124)

find string s2 containg s1 permutation, the blog is here.


Sixth interview (105 minutes)

Suggest a char with maximum occurrence at the position with the given prefix. The blog is here.

breadth first search algorithm - processed by layers. The blog is here.


Seventh interview (96 minutes)

union find algorithm is documented here.


Eighth interview (116 minutes)

Leetcode 91 Decode ways is documented here.

Isomorphic strings is documented here.

Extra algorithms discussed:

1. Second mock interview

My past practice on dynamic programming is here. Manhantan 2 booking woman is the algorithm to apply dynamic programming.

2. Ask code review for my mock interview performance on trapping rain water.

3. Discussion about hard level algorithm maximum disjoint subtree product

Get lost in a depth first search, DP, tree algorithm again

May 31, 2018

Introduction

It is my favorite thing to do if I have luxury to spend a few hours. I like to learn the algorithm again called Maximum disjoint subtree product.

I read my own blog written after the contest in May, 2017. I read the code I wrote in the contest, and I like to make any point above zero. I wrote more than one hour and three hundreds of lines code, but I still scored zero. The hard working spirit really touchs my heart again.

I do have to get a coach and learn better way to think in terms of depth first search, dynamic programming and tree.

Algorithm study

Here is the code I spent time to play with. I need to get some help from my coach. I like to learn how he solves a hard level algorithm.

Getting smart after 12 months

May 30, 2018

What I like to do is to solve a subproblem first. Assuming that there is an array, we need to find two disjoint subarray with the maximum product. I like to define two dynamic programming solutions, and then I solve the problem first.

Here is C# solution I write. Time complexity is O(N), N is size of the array.

Leetcode 205: Isomorphic Strings

May 31, 2018

Introduction

It is one of my mock interview algorithm given by my coach. I wrote a C# solution. I got hint to use array instead of using hashset.

Follow up 

July 20, 2018

I ran the code against Leetcode online judge using Leetcode 205. There is index out of range error for test case: "13", "42"

Need to fix the issue. The C# code is here to pass online judge. 

Cassadra Netflix case study

May 31, 2018

Introduction

I like to spend 30 minutes to study Cassadra Netflix.

Learning is so surprising. Originally I plan to read grokking system design lecture notes, and then try to memorize the solution.

But surprising my friend offered me coaching and then I had chance to go over complicated web architecture by first hand sharing. I was asked to read Cassadra Netflix after May 30, 2018 one hour coaching.

To be a good student and be coachable, I find that I am so enjoying to read Cassadra database and totally forget the time.


Scaling Time Series Data Storage — Part I


Reading is getting hard.

https://docs.datastax.com/en/cassandra/2.1/cassandra/dml/dml_manage_ondisk_c.html

write down new terms I need to learn:

Log-structured Merge Tree vs B-Tree

Read-before-write

statement: Cassandra never re-writes or re-reads existing data, and never overwrites the rows in place.

hard disks (HDD)
solid-state disks (SSD)

Being an interviewee : Insert intervals

May 29, 2018

Introduction

It is the interval algorithm but it is not easy for me to come out elegant idea to write simple code. I had some ideas, but before I came out the idea, I already wrote the code. The interviewer told me stop, and told me that I should make it simple.

Ideas 

Here is the transcript of the mock interview.

Hints pouring down 

I like the interviewer. He just quickly coached me through mock interview. I like to exaggerate how he did. He poured down hints one by one. I really like young talent Chinese graduate student, how hard he works, and he is willing to coach me. He did 3 times mock interviews with me, and this is the third time. I like his good collabration skills. I do believe that the future will be better with those young gradautes.

A few hints are given by the interviewer and the interviewer helped me to get the optimal solution and also very clean implementation:

1. About inserted interval, it can be replaced by current visited element
2. inserted interval can be replaced by the merge interval of two overlapped intervals.
3. Write simple code, I wrote the code to check next interval and logic is too complicated for the interviewer to follow. It may work, but the interviewer told me that it is better to discuss with the interviewer first.
4. The interviewer told me that it is better to ask hints, instead working on complicated solution. I do not totally agree on this.
5. If I am too busy to work on the code by myself, the interviewer may not have chance to work with me.

Follow up 

I wrote C# code and also I found a bug. Actually if I check my coding style and I should find the bug. Those two lines of code with variables insertedStart, insertedEnd, the scope should stay inside for loop. Now they are moved to line 60 and line 61.

Leetcode 94: Binary Tree Inorder Traversal

May 29, 2018

Introduction

I could not believe that I finally can write working solution using recursive solution today. It is quick and fast. I still remembered that I did choose to write a recursive solution, instead I wrote an iterative solution with some bugs on important meeting. This past 12 months I definitely have done some good training. I CAN write a recursive function very easily on binary tree.

I like to submit as many algorithms as possible on Leetcode.com.

Recursive solution

Here is my recursive solution.

Iterative solution

I like to go over the algorithm with tag stack. I wrote an iterative solution using stack, and it is good workout for me to master stack algorithm one more time.

Leetcode 91: Decode ways

May 29, 2018

Introduction

It is my eighth mock interview from my coach starting from 8:00 AM to 9:40AM on May 29, 2018. He asked me to work on Leetcode 91: Decode ways.

Mock interview

Here is code I wrote in the mock interview.

Follow up

I wrote the C# code and then tried to pass online judge. I made a mistake to put 0 which should be '0' on line 80.

Coach's advice

Please consider to define the array using extra one space. Let the first element of the array be empty, therefore in your solution line 80 index >= 1 can be removed.

Follow up 

May 2, 2019

I chose one of online mock interview on Leetcode.com and had chance to practice the algorithm one more time.

I spent 30 minutes to write and used debugger to help me to fix a few bugs in order to pass online judge.

Here are highlights:

91 Decode ways
I came cross three bugs and I had to use debugger to help me to figure out
1. mix char with integer, s[i] - '0' is to convert to integer
2. all results are zero, forget to increment one for the start
3. apply step 1 for all instances, miss a few place
4. missing edge case, tenth digit should exclude 0, 3 to 9. 0 is not considered by mistake.
5. missing edge case, 00 is not valid

And the code written is here to look up.

Deliver results

May 28, 2018

Introduction

It is one of Amazon leadership principles. I like to learn from the Amazon leadership.

Hava backbone: Disagree and commit

May 28, 2018

Introduction

It is one of Amazon leadership principles. I like to spend at least 30 minutes to study the principle first.

Dive deep

May 28, 2018

Introduction

Dive deep is one of Amazon leadership principles. I like to learn the principle and plan to spend 30 minutes at least.

Earn trust

May 28, 2018

Introduction

Earn trust is one of leadership principle. I like to spend 30 minutes to write a blog for this principle.

Frugality

May 28, 2018

Introduction

I like to write a blog for frugality principle. I think that frugality is hard to practice, it takes a lot of wisdom and determination. I like to apply the frugality principle to my daily job.

Bias for action

May 28, 2018

Introduction

I like to write a blog for Bias for action principle. I will start to work on it 10 minutes first.

Find a system design coach

May 27, 2018

Introduction

I had this past Saturday system design study, I had a few times to feel so tired and sleepy. I know that I may have problems down the road. I need to find a coach. I start to search who will be my best coach.

First two hours learning 

May 28, 2018

I just could not believe that I had two hours training from my friend. Two hours learning makes big difference.

Here is my notes I took in the training.

Second time coaching

May 29, 2018

It takes time for me to get ideas how things work out. I need to work on one thing a time. That is the reason I got a coach No. 3, who has a lot of industry experience. Basically he went over grokking system design lecture notes and discussed with me. If I have any question, he gave me answers and make sure that I can understand the concept by his explanation. He could explain things so clearly and I totally quickly understand.


Content dilivery network:  CSS, spritemap

Amazon S3/ cloudfront

CDN -> Amazon /cloudfront

Shard -> horizontal/ row/ databases
range-based shard

sharding - horizontal, columns
Direct-based partition
partition key values
Index - sacrife the space to get shortest time
Explain SQL plan -> look up index needed or not
Proxy - reverse proxy
enforce/ request/ rule/ login information / map/ API - url reroute

Queue - RabbitMQ, producer/ consumer

Data/ service   logging shipping/ database server
microservice
Horizontal
encyms   Deployment/ encyms

SQL/NoSQL JASON    redis
NoSQL, structure/ unchange
Cassandra/ couchDB

HDFS or cluster FS

RAID - redundant array of independent disks

I/O in parallel - read/ write

RAID - cluster / Redundancy

I was strongly advised to look at open source tool called Swagger / OSI open specification

Go over netflix stream system design

7.  File processing workflow
8.  Data Deduplication

2. Range based partition

10 caching   Least recently userd (LRU)

RAID - partition key -> 256 buckets
Blob - save image

Elastic search - NoSQL search , document - tuning score, criterias: two words how close they are, subject

high speed cache - google CDN

8. Metadata sharding
Partition
user id    cassandra

Memcache   k-V memcache


Given an example about tag on video, threshold > 3,
caching 20%

Redis - can be applied to anywhere
Cluster -
Elastic search
Cassandra - big data handling, very good write speed
build index x ( problem to build index)


Storage - log/ by minute/ 60 seconds
search

Overall, learning is much better with a friend to go over the system design of Netflix stream, and I had chance to ask a few questions. I was not afraid to ask questions, and then the friend gave me very good experience based on his work experience. The time spent is 60 minutes.


My task is to understand those tools, and be able to freely apply them in the system design. Redis, swagger, Elastic search, Cassandra, load balancer, Amazon/ Google/ F5 load balancer. The coach shows me how easily he can come out ideas how to design step by step.

Sascha Bajin - my favorite coach

May 27, 2018

I like to learn from the coach and then share with my coach of algorithm, a young Tsinghua university graduate.

https://www.youtube.com/watch?v=1D_bj0YFEWc

Darrell Cahill - coaching philosophy

May 27, 2018

Introduction

One of things I like to do is to do some research and help my coach to give me coaching time. I like to write down notes from this three minutes coaching video. After that, I will send my coach an email.

https://www.youtube.com/watch?v=LyRJ5IvWjss

Best coach I knew and met in China open 2017

May 27, 2018

Introduction

I like to share some document with my algorithm and data structure coach. So I like to share this great coach talk video.

https://www.youtube.com/watch?v=LyRJ5IvWjss

https://www.youtube.com/watch?v=Pd5HRQWzB0I

Work with my coach (II)

May 27, 2018

Introduction

I need to write an email to my coach today. He gave me a coaching lesson this morning 8:20 AM to 10:20 AM. He did good job to coach me tough algorithm.

I need to send him a good video about Safarova about her coach - my favorite one Rob Kentaley.

https://www.youtube.com/watch?v=oI4ug17z1kA

union find algorithm - 7th mock interview from the coach

May 28, 2018

Introduction

It is my most favorite algorithm called union find algorithm. My coach asked me to solve the algorithm to find maximum group. We had discussion around 100 minutes. Through the discussion, the coach showed me how to do time complexity, and then we had good time to discuss a few topics. At last, I asked the coach to write two function, one is to quick find, one is to union.

Transcript

Here is the transcript of mock interview on May 27, 8:00 AM.

Follow up

I spent a few hours to review my past practice on this union find algorithm, and then I wrote C# code for review. Also I was asked to write a depth first search algorithm, and I will write one.

Breadth first search distributed algorithm - 6th mock interview from the coach

Introduction

It is my most favorite algorithm May 2018. I was surprised to spend more than one hour to write the C# code and also fixed my original design issue. My design was kind of weak until I tried to test the third test case with 4 x 4 matrix. I found out the answer is not correct. For some reason, the current layer of node will get into next round when I apply breadth first search. Later, I added a hashset to exclude the current layer node to get into next round.

The algorithm is so ineresting and I remmebered that I worked on the similar algorithm called shortest distance to all building.

Algorithm 

I wrote a breadth first search algorithm based on my coach's hint. Find all elements in the matrix with zero value first, put all of them in the queue, and then process breadth first search on those elements in the same time.

It is kind of distributed algorithm. I like the challenge. I feel excited after I complete the algorithm.

Here is my mock interview transcript.

Here is my C# code after mock interview.

System design

May 27, 2018

Introduction

It is time for me to read grokking system design articles. I spent a few hours this Saturday and I read a few system design, one is instagram design.

What I like to do is to design some drills to help me read carefully, think carefully, learn something as well.

It is not easy for me to learn something if the content is not very well prepared. So I chose to purchase grokking system design with payment over $100 Canadian dollars. I like to focus on the lecture notes and do some research based on the reading material.

Argument of day

Julia, do not be silly. You work so hard and finally can do very well on algorithm and data structure problem solving. Then you should work hard on system design. It should be easier compared to algorithm and data structure.

Prepare some notes, follow a few simple steps.

Study notes

Think big

May 26, 2018

Introduction

It is my favorite thing to write a blog for one leadership principle called think big. Thinking small is a self-fulfilling prophecy. Leaders create and communicate a bold direction that inspires results. They think differently and look around corners for ways to serve customers.

Word by word

leaders -> directions -> results
customers -> serve customers -> ways to serve customer ->  look around corners for ways ...

a bold direction -> how to define a bold direction?

Relate to my experience

First I like to read the engineer's blog about Think big. Here is the link.

Insist on the Highest Standards

May 26, 2018

Introduction

It is time for me to learn leadership principle one by one. I like this one most since I know the difference to insist on the highest standards. 

Leaders have relentlessly high standards - many people may think these standards are unreasonably high. Leaders are continually raising the bar and drive their teams to deliver high quality products, services and processes. Leaders ensure that defects do not get sent down the line and that problems are fixed so they stay fixed.

Principle wording

rentlessly - 

high standards

unreasonably high 

leaders are continually rasing the bar

their teams to deliver high quality products, services and process

Insist on the highest standards

- highest standards -> what is the standards? how to define the standards? highest? How about high -> higher? 

leaders vs many people 

leaders -> their teams -> deliver high quality products, service and processes. 

How do leaders make the transition from insisting on standards level to delivering high quality ...

Relate to myself

I need to hold on highest standards. 

1. Push myself to master C# programming language from my own ranking 6 or 7 to 9. What I do is to read the C# book, ask questions, and memorize API. 

Every time I write C# code in mock interview, I ask question what problem I have on C# coding. I like to learn C# by checking the thinking process of basic problem solving. 

2. I like to ask questions on code review website and also make sure that I can easily get help if I need to work on some algorithm. I need to find out areas I can improve on C# code. 

3. I like to keep writing code every day, this way I can master the data structure and algorithm one by one. 

4. I believe that once I master the data structure and algorithm, I start to know how to make the products I architecture and code to high quality. 

Security - against attack

Code - readable, clean code

Code - simple code 

Code - object-oriented principle - try to apply to my own work 

Test coverage - 

Highest standards

- relate to my practice on Hackerrank contest, I continuously worked on the contest until I got my first gold medal. I documented every practice so that I review and find things to work on. I also try to train myself. 

- 

Highest standards 

Hire and Develop the Best

May 26, 2018

Introduction

It is important that I have a friend who checks with me daily about my progress about leadership principle study. We have short chats through Facebook messengers. We started to chat more about leadership since I started to work with my coach. The friend used to be my hitting partner to work together on algorithm a few times. 

Hire and Develop the Best

Leaders raise the performance bar with every hire and promotion. They recognize exceptional talent, and willingly move them throughout the organization. Leaders develop leaders and take seriously their role in coaching others. We work on behalf of our people to invent mechanisms for development like Career Choice.

Understand the leadership principle first

Let us go over terms in the principle. 

raise the performance bar

every hire and promotion

recognize exceptional talent

exceptional talent -> how to recognize, how to measure exceptional? talent? what talent? basic talent or special talent. 

Leader move them throughout the organization. 

Organization -> business -> what kind of management in the business? 

Leaders vs coaches -> coaching others -> what motivations stay behind? 

on behalf of our people to invent mechanisms for development like career choice. 

It is hard to relate to my own practice. 

Please list a few mechanisms for development like career choice. Career choice, what other options do we have besides career choice.

Relate to my personal story

I hired best coach for my data structure and algorithm since May 12, 2018. I start to build some experience to have a good coach.

Follow up 

Oct. 18, 2019

Back in May 2018, I decided to hire a personal coach from one of top performers I met through pramp.com. I practiced over 300 times, and then one of players has super performance. He was a graduate student in Tsinghua university. So I decided to ask his help to prepare onsite interview from Amazon. 

Learn and be curious

May 26, 2018

Introduction

It is my most favorite topic of leadership principles. It is straightforward. Learn and be curious. As I am getting old, I do not see any improvement until I had chat with one of shanghai jiaotong university alumni - my classmate back in 2015. 

Learn and Be Curious

Leaders are never done learning and always seek to improve themselves. They are curious about new possibilities and act to explore them.

Learn and be curious

Do not learn. Do not be curious - the opposite is not good!

Leaders are never done learning and always seek to improve themselves. It may be a wishful thinking. It is hard to find time to learn and actually be able to learn. Seek to improve themselves. It is not 

easy to keep improvemnent. There is a plateau. Once you reach the plateau, it is hard for you to acquire new skills. 

Curious about new possibility - 

Act to explore them - 

How to apply sports coaching on this leaders or being leaders? 

I know that I have to stay to be coachable. It is hard for me to do that. Since I have to spend most of my time to learn the basics, work full time to make a living first. I notice that curiosity is ok but I have limited time. I have to find ways to get training on interview skills daily, get soft skills to be improved. 

I was coached in 2015 by my shanghai jiaotong university classmate from 1989 to 1992, who works for Simens in Michigan. I was told to take courses on pluralsight.com. I also try to get involve in the community as possible. I join Hackerrank community, I play contest, and post comment and also document my journal of practice. 

I learn from sports coaching. I follow all seeded tennis players. I learn from their up and downs. I start to follow them and get to know more sports traing, coaching and practice and drill, and I also attend the event, practice by myself as well. 

I like the individual sports like tennis. But it is not individual sports anymore. I like the way how the professional players handle the ....

I know that it is important to be competitive in tennis sports. I know the difference. If I walk on the tennis court, people will come to me and offer me a practice together. 

Are Right, A Lot

May 26, 2018

Introduction

It is time for me to do some study on leadership one by one. It is not easy to come out the principle, but it is also very hard for me to look up those principles without a few good references. 

The principle is called Are Right, A Lot. The explanation is "Leaders are right a lot. They have strong judgment and good instincts. They seek diverse perspectives and work to disconfirm their beliefs."

Leadership study

Are right, A lot. 

Let me brainstorm the leadership on May 25, 2018.

Leaders are right a lot. This statement makes sense or not? Leader are right a lot. A lot means bigger than 50% probability, 70% is a lot? 

Judgement and good instincts. Question is how to define judgement as strong, how to define instincts are good. 

It is hard to mainain the strong judgement. Since bible says that do not judge otherwise you will be judged. 

Good instinct? Sometimes we have to practice a lot, meet a lot of people through mock interview, and then I can quickly learn how to make good judgement. Sometimes it is easy to tell that the peer is nervous, or trying to hide lack of practice, sometime the peer tries to get hint without asking. 

diverse perspectives? Give an example about diverse perspective, 

Work to disconfirm their beliefs.

Relate to my work experience

I have to work on some way to help me get motivated and keep getting help from various resources. I need a few platforms for me to play and get recognition for the hard work, knowledge about computer science, and good working spirit and easy to collaborate.

I need to brand myself. I need to work on daily and try to put together things. 

Work with my coach

May 26, 2018

Introduction

I like to spend some time to work on my coach training, and I like to share my research with my coach this weekend. Since we like to get close, I can have more ideas to learn from his coaching.

Write a short email first

I spent time to write one email after my last mock interview. The coach does not get impressed. He replied. So I wrote another one.

Hi, Mr. xxx, 

 I like to spend give five minutes to 10 minutes to share my favorite tennis sports. I like to find out ways to win.

 Sloane Stephens, rank from 974 to 17 since she won grand slam. She had foot surgery, training again, very good story to share, encouraging, USA style success story. 

 When is our next meeting? I will find time to work on my home work before our next meeting. 

I did send another email since I sent a wrong link of youtube:

Hi, Mr. xxx, 

Sorry, I sent wrong video. I like to share one video from USA athlete Sloane. 

I like to send this video from Sloane Stephens - https://www.youtube.com/watch?v=b1QM5cjlh_w

I like Sloane's coach, and her coaches and how they work together. 

Being coachable 

I like to work on small details to make myself a good student and allow my coach guide me better to solve algorithm and data structure problems. It is second week I got a coach. 

The coach told me to work on easy algorithm on Leetcode.com.

100 minutes to work with a young graduate - Copy linked list with random pointer

May 26, 2018

Introduction

I could not believe that I spent over 100 minutes to work with a young graduate on my May 25, 2018 10:00 PM mock interview. It was such great experience, I learned how to evaluate his performance and gave him honest feedback.

First Algorithm - copy linked list with random pointer

I will come back to write down more.

Second algorithm - Maximum subarray product

I will come back to write down more.

Being an interviewee: Suggest a char with maximum occurrence at the position with the given prefix

May 23, 2018

Introduction

It is my most favorite algorithm to practice with my coach. The algorithm is called to suggest a char with maximum occurrence at the position with the given prefix.

The coached asked me if I have Trie experience two days before my mock interview, so I spent some time to review Leetcode 212 and also my question on stackexchange.com.

The conversation of writing a Trie data structure was very interesting.


Coach: can you explain how you define the Trie?
Julia: It should be recursive structure, Children should have Node type as well.
Coach: Do you need to have a list of numbers for children?
Julia: No. It should be minimum. Every node just takes care of its own number.

In-between the mock interview, the coach asked me why you define the Trie this way, save "ABC" as a member of class definition. I just told the coach that I memorized the solution I reviewed recently. But actually we do not need to do that here. I felt much more relax after we work together more than 10 hours.

Trie algorithm

I learn how to work with the coach and write a solution in the mock interview. And also the coach asked me to test the code using the test case documented from line 93 to line 96, I found the bug on line 107, and delay increment of index variable until line 123.

Here is the transcript of the mock interview.

Follow up 

I wrote the C# code and tested it using a simple test case. Now it is 12:21 AM, I need to rush to go to bed since at tomorrow 8:00 AM I will have a mock interview.

10:00 PM mock interview as interviewer

I also ask the interviewee to work on the algorithm at 10:00 PM mock interview. The intervewee has more than eight years experience working in Silicon Valley to target for biggest software companies, and I helped him to write a Trie solution. What I did is to try to copy my coach, how he did to me. I asked the interviewee to work on the test case, show me the trie, and also give hint to use array for fixed size instead of using Dictionary.

Here is the C# code the interviewee wrote before I write my own C# solution.

Code review from my coach

I sent an email to ask the coach to review my code before I will have next mock interview. The coach offered me to send the code before mocking interview after our second mock interview, so he can prepare better for next mock interview. We can squeeze in more activities in the mock interview together. My coach is super talent programmer and I like his working attitude.

"I think that it is definitely no problem at all. Let us meet Friday morning.

I just like to send you the code I wrote for suggest char based on prefix.

Here is the link."

May 25, 2018
8:00 AM

My coach told me that one thing is not correct. The iterate variable may be null pointer. I need to add null pointer checking on line 152.

Being an interviewee: Leetcode 42: Trapping rain water

May 23, 2018

Introduction

I asked my friend to give me a mock interview and he offered me to practice mock interview Tuesday and Thursday and Friday for 45 minutes each time. He did very good job to ask me to work on Leetcode 42: Trapping rain water. He also gave me some good advice, but he gave out the major hint too quick so that I did not have to come out the solution by myself.

I was nervous and talked about brute force solution, and then talked about descending stack. I made a mistake to try to relate to the algorithm I practiced recently. This is a bad behavior, the interviewer had discussion with me at the end of mock interview. I should get rid of this non reasoning thinking, I am supposed to work on the algorithm I have never seen before. So I have to practice my approach based on the facts, test cases, intuition etc.

The solution is nothing to do with descending stack, but the interviewer just gave away the major hint. He told me to scan two times, one is from left to right, the second one is to scan right to left.

Mock interview 

Here is the transcript of the mock interview.

Follow up

After mock interview, I wrote a C# solution. Here is the link.

Ask help from my coach in Tsinghua university

I sent an email to my coach to ask help on May 25 12:20 AM:

I am glad to find you as my coach. Here is the algorithm I mocked interview Tuesday with Mr. Yang. I did not do very well on analysis, take a look if you have a few minutes.

Here is the blog link.

I have to call it a day. Talk to you later.

May 25, 2018
8:20 AM
The coach told me that I did not have time to develop the solution using descending stack. Actually the rain water is filled up for each time range incrementally. He explained the algorithm to me based on given test case, I understand the algorithm right away.

Basically there are multiple ways to solve the algorithm, my interviewer only knows one way to solve it.

I will write C# solution based on descending stack later.

Find string s2 containg s1 permutation - 5th interview from my coach

May 23, 2018

Introduction

It is the algorithm called find string s2 containing s1 permutation. I wrote the algorithm using sliding window, and also implement the algorithm using time complexity O(N) where N is the length of string s2.

Algorithm

Here is the transcript for my mock interview. We used Google Docs.

I wrote the code but there are some issues in my code. The coach spent over 5 minutes to test my code using a test case, and then he shared with me his implementation using time complexity O(26*N) solution.

Here is my C# algorithm I wrote after the mock interview.

Invent and Simplify principle study

May 22, 2018

Introduction

It is the principle called Invent and simplify principle. It is my favorite. Here is the explanation. Leaders expect and require innovation and invention from their teams and always find ways to simplify. They are extremely aware, look for new ideas from everywhere, and are not limited by "not invented here". As we do new things, we accept that we may be misunderstood for long periods of time.

Principle study

Let me write down some keywords in the above principle here:


innovation and invention
find ways to simplify
aware and look for new ideas, also from everywhere. Everywhere is the keyword.
new things
may be misunderstood for long periods of time

long periods of time - how long? one week, one month, one year?

S.T.A.R story

It is my favorite principle. I have so many things to write down.

I look for ways to learn how to write simple code, readable code.

Action: I asked questions on stackexchange.com, I start to write on quora.com, Leetcode discussion panel, my own coding blog.

I practice mock interview daily, understand how others do the work as software engineer, learn to evaluate the talent, learn one soft skill a time.

I practiced one algorithm over 50 times. I have written one algorithm in mock interview over ten times.

New things I tried last 5 months:

Udemy.com
...

Result:

will seen the result one day.

Ownership principle study

May 22, 2018

Introduction

It is my task to write a short blog about Ownership principle. Here are the detail about the ownership, leaders are owners. They think long term and don't sacrifice long-term value for short-term results. They act on behalf of the entire company, beyond just their own team. They never say "that's not my job".

Here are the words in the above statement:
Leaders, owners,
long-term value  vs short-term result
entire company   vs their own team
That is not my job

Study note

I like to study the leadership one a time.

If I like to apply the principle to my current job, what is the case?

Long-term value vs short-term result

Long-term value - I try to rewrite the website to make sure the code is readable, remove smell of code, write simple code, break giant function or object into small objects. Apply object-oriented design.

I plan to study those courses on frontendmasters.com about web security, and I learn how to use Google web browser developer tools.

Short-term result - visual things to do, visual evidence I do the work. Something surface level.

This is not my job - Have I said that sentence before?

S.T.A.R story

I like to come out a few stories related to ownership.

Source control

S  - Situation - Virus issue on my computer, ransom attack
T - Task - I need to figure out better way to do source control
A - Action - last August I started to purchase github service annual subscription. I did some research on source control available products, and then I chose to subscribe the github.
R - Result  - The source control is advanced to much better status compared to before.

Web server and database migration

Anti virus software incident 

S - Situation - false positive, the anti-virus software deleted database file
T - Solve the issue - restore the database
A - Restore the website
      Study the virus and anti-virus, and ask questions about false positive issue
      Need more work here ...
R - Result
   

Website onwership

I need to balance my time on different issues, front end, use interaction, website architecture, SQL server administration, and all related issues.

A list of things happened:

SQL injection attack

Virus software removed the database file

Database server and web server migration

Work with consultation company to upgrade the database server, IIS server

IIS 8.0 learning

C#, JavaScript, HTML, CSS, Jquery coding

Vacation break challenge

Work with sales, marketing and graphic design

Move source control to github after ransom attack, server upgrade etc. in 2017.

Business analysis ownership

Sales analysis or any analysis, how to handle dispute? The program I write and design I have to make change after 2015, if there is any dispute, I should be able to set down the dispute in less than 5 minutes.

From Julia coding blog to self-training course on udemy.com

May 21, 2018

Introduction

It is the holiday and then I tried to do something creative. I like to prepare for a course on udemy.com, the course is titled "From Julia coding blog to self-training course".

I have a list thing to do before I can submit the course for a review.

Things to work on

Here is the things to work on. I am planning to find time to work on 30 minutes a time.