Binary tree root to leaf path minimum path value with the path

Nov. 15, 2017

I like to document my mock interview practice on this algorithm. The topic is about analysis of the algorithm, how to reason to find possible bugs?

Here is C# practice code.  I added line 27 to line 32 to fix the bug since the peer told me that the edge case with no children. The advice from the peer is "After writing the code need to analyze more before running it". 

Story of analysis

I need to explain how the depth first search works since peer asked if I should add an argument of function to pass the existing value. I did explain the algorithm in the mock interview, but the peer felt that he did not know C# very well and got confused. 

I like to write my story to show how I analyze the algorithm after the mock interview, try to make the explanation to a very good one. 

Let us go over  a tree with the following nodes:

      0
  /   |   \
 4   3   6
 /
3

The depth first search algorithm can be solved this way. The root node with value 0 has a tree, to find its minimum path to the leaf node, first if the root node is null, then value is 0; if the root node is not null, and if the root node has no children, it is a base case, the minimum path is the value of root. Otherwise, go over each children of root node with value 0, and go to each child in the array [node 4, node 3, node 6], and ask each node to get its minimum value for the path, denoted as Mi, and just add root node value 0 to Math.Min(Mi, i from 0 to 2).

Miss a base case

From the above paragraph, I highlighted the base case I missed in mock interview using brown color, and the peer had to tell me that there will be a problem if there is no children. In other words, in the tree showing in the above diagram, if the root node with value 0 has no children, it is a base case, the minimum path is the value of root.

Order string (VII)

Nov. 15, 2017

I like to write a blog about this C# practice, using Linq IList.Sort method. The link is here.

Order string (VI)

Nov. 15, 2017

Algorithm Study and Code Review

Here is the code related to the algorithm. I like to write a blog on the code. The main idea is to use primitive type string, just add index to the first element of string array, avoid a struct or a class definition. Kind of tricky. 

Follow up study 

Nov. 16, 2017

It is always a good idea to search code review to read IComparable<T> code review. I sepnt over 20 minutes to read the algorithm: Dynamically sorting with IComparer. And one of statement in the code review reads like the following:

This

public int CompareTo(ProductSortAttribute other)
{
    if (this.Index == other.Index)
    {
         return 0;
    }

    if (this.Index > other.Index)
    {
         return 1;
    }

    return -1;
}

can be shortened to

public int CompareTo(ProductSortAttribute other) {
    return this.Index.CompareTo(other.Index);
}

Since Int32 also implements Comparable<T>.

What is Int32?

Here are a list of things Julia starts to her independent study:
1. What is Int32? A structure
2. What interfaces does Int32 implements? IComparable<T>, IFormattable, IConvertible.
3. Where is the source code of Int32 in mscorlib? Link is here.

Comparable <T>  study

Sometimes, it is so easy to find an excellent lecture notes, and then I can follow quickly how to write basic comparer. Here is the one.

Order strings (V)

Nov. 4, 2017

Introduction

It is fun to continue to work on C# practice on this algorithm called order strings.

I reviewed the code and made some change, C# code is here for me to review later.

Order string (IV)

Nov. 14, 2017

Introduction

It is my favorite C# code to study, through the code, I can tell that the player has more C# coding experience compared to me, and also the trick used to do numeric comparison to make code so simple and only take one line of code, referring to line 44.

I just could not believe that the experience the player has and it makes coding so enjoyable experience, like a competing sports.

I could not express more enjoyment to read other people's code. When I read those excellent engineering idea, creative idea to solve the problem, I cannot believe that it makes coding such a challenging sports and I am just glad to be a follower.

Code study

I reviewed the code and rewrite the code, here is the code. I have to push myself to get LINQ to my daily coding practice, so I am ready one day to write a web application with much better code using LINQ.

Relax your mind 

I like to use this video to relate to read an excellent engineering idea to deal with solving problem.

Look who we meet today while doing jet ski ride😍This animals are pure beauty,intelligence,strength and spirit🐬❤️🙌Это была неожиданная,но настолько приятная встреча🐬❤️🙌Обожаю дельфинов,сразу вспомнился Детский стишок в школе- Друг за другом мчится стая, Волны телом разрезая,То хвосты, То снова спины, Кто вперёд, Плывут Дельфины 😍🐬 #Maldives #exploring #dolphins #wildnature #какпрекрасенэтотмир #дельфины #встречавоткрытомокеане

A post shared by Elena Vesnina (@vesnushka86) on Nov 13, 2017 at 3:31am PST

Order string (III)

Nov. 14, 2017

Introduction

It is the best time to learn C# programming using one of medium algorithm in the Morgan Stanley codesprint. The design of algorithm includes using BigInteger class and also LINQ OrderBy and OrderByDescending.

Code study

I reviewed the code first, and then I rewrite the code. C# code is here.

Order strings (II)

Nov. 14, 2017

Introduction

It is time for me to learn how to write a C# program and also review other's code. The second study code is written using SortedDictionary. DescendingComparer class and DescendingComparerI class are defined.

Code design talk 

Here is the C# code after I review the code.

Order strings (I)

Nov. 14, 2017

Introduction

It is the time for me to study code submission using C#. This is the first C# code submission I studied, delegate is the keyword used in code, and also string.TrimStart.

Here is the C# code after I reviewed the code.

Code design talk 

The structure is used and called OrderString.

structure  OrderString
{
    public int      Index;
    public string Lexicographic;
}

Pluralsight.com - becoming an outlier

Nov. 13, 2017

Introduction

It is such a great privilege that I got subscription of pluralsight.com monthly. It is time for me to review how many hours I spend on pluralsight.com last 12 months.

I like to revisit the course called becoming an outlier: reprogramming the developer mind by cory house.

Course study

Plan to take some notes and do some research from lecture notes.

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>.