Nov. 27, 2016
Try to post the first code review on code review on stack exchange, code review section.
When I try to put the title:
Leetcode 329 Longest Increasing Path in a matrix - DFS, memorization
Here are information coming out.
Questions that may already have your answer
Review the above entries.
So many to read and so good the experience is. Cannot wait to spend time on those posts. Julia knows that it is time to make changes, her research usual touched the surface only.
For example, with stackexchange code review, her research from Nov. 30 posting the question to a perfect solution (Dec. 2, 2016) on Java TreeSet class floor method and its analog in C# ends up working code - SortedSet GetViewBetween, score maximum score. It takes less than 3 days to find a practical solution, with two experts' help.
Blog reading:
Bear and steady gene - C# algorithm:
https://gist.github.com/jianminchen/153eab0defae014842e8
Sunday, November 27, 2016
Saturday, November 26, 2016
Tennis sports and interviews
Nov. 26, 2016
Julia likes to play competitions on HackerRank in 2016, whenever she has problems, dealing with strategies, emotions, specially not good performance, she turns to tennis sports, and starts to study more tennis players, coaches; and try to find some great ideas.
This Saturday, she went through a few tennis interviews, and she learned something new. She likes to write down some notes:
1. Most favorite one - Nick Bollettieri - 84 years old, tennis coach,
(birth certificate has problem, should be 48 years old, not 84 years old. Age is just a number.)
https://www.youtube.com/watch?v=vQPo2firzjU&t=331s
Put next point, last point away, be able to control the emotions.
Coaching philosophy:
Be Conservative and Predictable. Be very gentle on first few minutes, you never know what happens to the player.
Work with young kids.
You cannot predict what will happen.
Genie Bouchard,
Talk about taking advantage of health, brought her to see young kids with cancer in hospital.
Respect the opponent, respect the crowd, children are watching you.
What is most important point? Next point.
Put forward, move forward.
Great acting man, are you in control?
Mind catches his talent, he can be a dangerous player.
Nick Bollettieri, Tennis Legend: Talks at GS Session Highlights (Goldman Sachs)
https://www.youtube.com/watch?v=UUxrQs0vzgk
Be able to read people;
Stop law school, back to tennis coaching. Coach almost 10 top one players.
Refuse to lose;
To be a winner, 24 hours job.
Talent, hard work, sweat?
What do you think it makes a good coach?
1. Listen
2. Do not say I cannot do it.
3. Success comes after team work.
Share up-time, share down-time.
80 years old, gave the speech:
1. Make every people feel respected; treat door man, garbage collector very well.
2. Can do attitude
2. Nick Kyrgios - young, 20 years old in 2015,
https://www.youtube.com/watch?v=NR-DwUwcpcs
Relax, will not get too angry;
Do everything you can, you can control.
Talked about home sick, his dad came to live with him on the tournaments, cooked for him.
3. Milos Raonic
4. Lucie Safarova - rising star
https://www.youtube.com/watch?v=KZ1i9Q6nt-U
5. Timea Bacsinszky
https://www.youtube.com/watch?v=fRnWJVXgNtk
She talked about her study on hotel management, and did some work on the kitchen at work. But she came back to tennis sports.
Julia likes to play competitions on HackerRank in 2016, whenever she has problems, dealing with strategies, emotions, specially not good performance, she turns to tennis sports, and starts to study more tennis players, coaches; and try to find some great ideas.
This Saturday, she went through a few tennis interviews, and she learned something new. She likes to write down some notes:
1. Most favorite one - Nick Bollettieri - 84 years old, tennis coach,
(birth certificate has problem, should be 48 years old, not 84 years old. Age is just a number.)
https://www.youtube.com/watch?v=vQPo2firzjU&t=331s
Put next point, last point away, be able to control the emotions.
Coaching philosophy:
Be Conservative and Predictable. Be very gentle on first few minutes, you never know what happens to the player.
Work with young kids.
You cannot predict what will happen.
Genie Bouchard,
Talk about taking advantage of health, brought her to see young kids with cancer in hospital.
Respect the opponent, respect the crowd, children are watching you.
What is most important point? Next point.
Put forward, move forward.
Great acting man, are you in control?
Mind catches his talent, he can be a dangerous player.
Nick Bollettieri, Tennis Legend: Talks at GS Session Highlights (Goldman Sachs)
https://www.youtube.com/watch?v=UUxrQs0vzgk
Be able to read people;
Stop law school, back to tennis coaching. Coach almost 10 top one players.
Refuse to lose;
To be a winner, 24 hours job.
Talent, hard work, sweat?
What do you think it makes a good coach?
1. Listen
2. Do not say I cannot do it.
3. Success comes after team work.
Share up-time, share down-time.
80 years old, gave the speech:
1. Make every people feel respected; treat door man, garbage collector very well.
2. Can do attitude
2. Nick Kyrgios - young, 20 years old in 2015,
https://www.youtube.com/watch?v=NR-DwUwcpcs
Relax, will not get too angry;
Do everything you can, you can control.
Talked about home sick, his dad came to live with him on the tournaments, cooked for him.
3. Milos Raonic
4. Lucie Safarova - rising star
https://www.youtube.com/watch?v=KZ1i9Q6nt-U
5. Timea Bacsinszky
https://www.youtube.com/watch?v=fRnWJVXgNtk
She talked about her study on hotel management, and did some work on the kitchen at work. But she came back to tennis sports.
Friday, November 25, 2016
HackerRank - women's codesprint - Prim XOR - after contest practice
Nov. 25, 2016
Julia spent over one hour to read the problem statement in the contest, but she could not do good research to find out the ideas to solve the problem.
Problem Statement: medium algorithm, maximum score: 50
https://www.hackerrank.com/contests/womens-codesprint-2/challenges/prime-xor
She likes to practice the algorithm very soon.
Julia spent over one hour to read the problem statement in the contest, but she could not do good research to find out the ideas to solve the problem.
Problem Statement: medium algorithm, maximum score: 50
https://www.hackerrank.com/contests/womens-codesprint-2/challenges/prime-xor
She likes to practice the algorithm very soon.
Thursday, November 24, 2016
Stack Exchange: Code Review - Julia's new school
Nov. 24, 2016
Julia started her first day to look into stack exchange: code review, and then, she joined one of discussion - quicksort, she was amazed how she learned quickly in the place.
Her first reading starts from here:
http://codereview.stackexchange.com/questions/5648/any-way-to-make-this-recursive-function-better-faster/5661?newreg=7b2fea2453a54c15bc466355fea0891d
Learn from expert on code review:
http://codereview.stackexchange.com/questions/142808/quick-sort-algorithm/142853#142853
http://codereview.stackexchange.com/a/142853/123986
Julia also wrote a blog about quick sort in 2016:
http://juliachencoding.blogspot.ca/2016/02/quick-sort-practice-makes-difference.html
Julia's favorite reading:
http://codereview.stackexchange.com/questions/77782/quick-sort-implementation?rq=1
Study stackoverflow profile:
http://codereview.stackexchange.com/users/507/loki-astari
Actionable Items:
Read more live discussion on stackoverflow code review sections, at least find 5 top talents in C++, and find 10 advises from them in a week.
1. First one: Loki astari
Study stackoverflow profile:
http://codereview.stackexchange.com/users/507/loki-astari
Julia's favorite learning on Nov. 25, 2016:
So let the compiler work it out.
-- end of learning --
Coding Style - Great advice on coding/ design, a hackerRank question:
http://codereview.stackexchange.com/questions/140825/keeping-track-of-the-tennis-score/140827#140827
Julia started her first day to look into stack exchange: code review, and then, she joined one of discussion - quicksort, she was amazed how she learned quickly in the place.
Her first reading starts from here:
http://codereview.stackexchange.com/questions/5648/any-way-to-make-this-recursive-function-better-faster/5661?newreg=7b2fea2453a54c15bc466355fea0891d
Learn from expert on code review:
http://codereview.stackexchange.com/questions/142808/quick-sort-algorithm/142853#142853
http://codereview.stackexchange.com/a/142853/123986
Julia also wrote a blog about quick sort in 2016:
http://juliachencoding.blogspot.ca/2016/02/quick-sort-practice-makes-difference.html
Julia's favorite reading:
http://codereview.stackexchange.com/questions/77782/quick-sort-implementation?rq=1
Study stackoverflow profile:
http://codereview.stackexchange.com/users/507/loki-astari
Actionable Items:
Read more live discussion on stackoverflow code review sections, at least find 5 top talents in C++, and find 10 advises from them in a week.
1. First one: Loki astari
Study stackoverflow profile:
http://codereview.stackexchange.com/users/507/loki-astari
Julia's favorite learning on Nov. 25, 2016:
-- start learning:
http://codereview.stackexchange.com/a/77821/123986
-
Compilers Job
Don't do work the compiler can do for you:int arr[8] = {110, 5, 10,3 ,22, 100, 1, 23};So let the compiler work it out.
int arr[] = {110, 5, 10,3 ,22, 100, 1, 23};-- end of learning --
Coding Style - Great advice on coding/ design, a hackerRank question:
http://codereview.stackexchange.com/questions/140825/keeping-track-of-the-tennis-score/140827#140827
Book reading: Java Puzzles
Nov. 24, 2016
Here is C# reading list:
http://www.informit.com/articles/article.aspx?p=1769249
One of books is Julia's new favorite, she read first 3 puzzles, she loves them. So, she starts to read the book one puzzle at a time.
Java Puzzlers by Joshua Bloch and Neal Gafter
More reading:
http://codereview.stackexchange.com/questions/5648/any-way-to-make-this-recursive-function-better-faster/5661?newreg=7b2fea2453a54c15bc466355fea0891d
Here is C# reading list:
http://www.informit.com/articles/article.aspx?p=1769249
One of books is Julia's new favorite, she read first 3 puzzles, she loves them. So, she starts to read the book one puzzle at a time.
Java Puzzlers by Joshua Bloch and Neal Gafter
More reading:
http://codereview.stackexchange.com/questions/5648/any-way-to-make-this-recursive-function-better-faster/5661?newreg=7b2fea2453a54c15bc466355fea0891d
Leetcode 300: longest increasing subsequence
Nov. 24, 2016
Motivated by the article reading:
https://blogs.msdn.microsoft.com/ericlippert/2004/07/21/recursion-and-dynamic-programming/
Julia likes to practice this Leetcode 300, and then look into various solution using dynamic programming.
First, write a C# program using recursive, memorization solution, using code in the above blog.
Motivated by the article reading:
https://blogs.msdn.microsoft.com/ericlippert/2004/07/21/recursion-and-dynamic-programming/
Julia likes to practice this Leetcode 300, and then look into various solution using dynamic programming.
First, write a C# program using recursive, memorization solution, using code in the above blog.
HackerRank - woman codesprint#2 stone division - recursive design study (series 5 of 5)
Nov. 24, 2016
Being a software programmer, Julia learned the lesson through this medium algorithm - stone division; she stumbled on it, struggled to make it work over 5 hours, she knew that she had to make changes.
She likes to do some research on recursive common mistakes, and then, further topic on recursive design concerns. After a few hours study based on Google search "recursive common mistakes", she felt that the study is still too weak. She likes to find some one with very strong technical background in industry, share ideas. So, with her research on stackoverflow recently, she started to look into who made contribution on stackoverflow on this topic. She found a lot to read.
Here is her research to find her something to read on this topic:
stackoverflow->
http://stackoverflow.com/questions/25676961/understanding-how-recursive-functions-work?noredirect=1&lq=1
->
http://stackoverflow.com/users/88656/eric-lippert (People reached: 10.8 million)
->
She found a top programmer, who designed C# in Microsoft and then work for facebook, and also she found the first article so helpful.
Julia likes the style of writing and she quickly identified that the article has a great teaching style.
https://blogs.msdn.microsoft.com/ericlippert/2004/07/21/recursion-and-dynamic-programming/
(Compared to Julia's sharing, two articles: first, she worked on leetcode algorithm, Leetcode 300: longest common subsequence, she blogged about it. second, she wrote on the dynamic programming, Lintcode 79: longest common substring, she also worked on it in 2016. )
Recursion series, more reading:
Julia's notes:
Part 0:
Part 1:
appear to be a circular definition, but it is really not. 'Spiral' definition
bottom out - base case
A binary tree is either:
inductive hypothesis -
Part two: unrolling a recursive function with an explicit stack
1 million nodes - balanced tree - 20 recursive depth - 2^10 = 1024, so 1 million is around 2^20
"anonymous locals" -
callee's frame - caller's frame - current activation frame
the temporary variables are spelled out
Part three: build a dispatch engine
With all that said, I haven't found any degree (at least from any school I've interviewed applicants for) to be a reliable signal for programming. Even if they went to a really good school, there's a good chance that they spent all their time learning network protocols and low-level mechanisms, and will happily write up a sliding-window implementation for me, but will stare at me blankly when I ask for a simple recursive algorithm. It's just tough to find people that spent time studying and practicing general-purpose computer science.
So, Julia reviewed the algorithm and wrote a more readable C# version to post a question on stackexchange.com.
Being a software programmer, Julia learned the lesson through this medium algorithm - stone division; she stumbled on it, struggled to make it work over 5 hours, she knew that she had to make changes.
She likes to do some research on recursive common mistakes, and then, further topic on recursive design concerns. After a few hours study based on Google search "recursive common mistakes", she felt that the study is still too weak. She likes to find some one with very strong technical background in industry, share ideas. So, with her research on stackoverflow recently, she started to look into who made contribution on stackoverflow on this topic. She found a lot to read.
Here is her research to find her something to read on this topic:
stackoverflow->
http://stackoverflow.com/questions/25676961/understanding-how-recursive-functions-work?noredirect=1&lq=1
->
http://stackoverflow.com/users/88656/eric-lippert (People reached: 10.8 million)
->
https://blogs.msdn.microsoft.com/ericlippert/2004/07/21/recursion-and-dynamic-programming/
->
https://blogs.msdn.microsoft.com/ericlippert/2004/05/20/results-of-the-fibonacci-challenge-are-in/
-> teach recursive
https://blogs.msdn.microsoft.com/ericlippert/2004/05/19/how-not-to-teach-recursion/
->
https://blogs.msdn.microsoft.com/ericlippert/2004/05/20/results-of-the-fibonacci-challenge-are-in/
-> teach recursive
https://blogs.msdn.microsoft.com/ericlippert/2004/05/19/how-not-to-teach-recursion/
She found a top programmer, who designed C# in Microsoft and then work for facebook, and also she found the first article so helpful.
Julia likes the style of writing and she quickly identified that the article has a great teaching style.
(Compared to Julia's sharing, two articles: first, she worked on leetcode algorithm, Leetcode 300: longest common subsequence, she blogged about it. second, she wrote on the dynamic programming, Lintcode 79: longest common substring, she also worked on it in 2016. )
Recursion series, more reading:
Julia's notes:
Part 0:
Part 1:
Teach how to think about recursion
recursive way to think about a list emphasizes the similarity of a fragment of the list to the whole list.
recursively define a list as either
1. the empty list with zero items on it, or
2. an item followed by a list
appear to be a circular definition, but it is really not. 'Spiral' definition
All recursive functions follow the same basic pattern:
Am I in the base case? If so, return the easy solution.
Otherwise, figure out some way to make the problem closer to the base case and solve that problem.
bottom out - base case
A binary tree is either:
an empty tree, or
a value associated with two binary search trees, called the left and right child trees.
inductive hypothesis -
Part two: unrolling a recursive function with an explicit stack
1 million nodes - balanced tree - 20 recursive depth - 2^10 = 1024, so 1 million is around 2^20
"anonymous locals" -
callee's frame - caller's frame - current activation frame
the temporary variables are spelled out
each recursion happens on its own line
Part three: build a dispatch engine
January 13, 2017
Julia worked hard on the blog study, and then, she found out the code review on stackexchange.com, and then she started to post questions on algorithms, and get connected to the community. And this is a break-through, finally Julia stepped out her lonely zone - blogging, practicing, contest, and get really connected to people with same spirit - volunteer and also community builders.
Feb. 23, 2017
Read the article about Google interview, and then read the comment from an ex-googler:
With all that said, I haven't found any degree (at least from any school I've interviewed applicants for) to be a reliable signal for programming. Even if they went to a really good school, there's a good chance that they spent all their time learning network protocols and low-level mechanisms, and will happily write up a sliding-window implementation for me, but will stare at me blankly when I ask for a simple recursive algorithm. It's just tough to find people that spent time studying and practicing general-purpose computer science.
So, Julia reviewed the algorithm and wrote a more readable C# version to post a question on stackexchange.com.
Wednesday, November 23, 2016
HackerRank - Woman codesprint#2 stone division - recursive intensive training (series 3 of 5)
Nov. 23, 2016
Julia failed on one medium algorithm - recursive function in the contest. So, she likes to get some training on the skill.
A few reasons she failed:
1. Extra work - Recursive function involves building a string first.
2. Time consuming - use StringBuilder, backtracking
3. Failed to pass second test case; idea is not correct.
Previous work intensive on recursive function:
Last time Julia learned recursive work intensively through HackerRank Linked List:
started from May 8 to , over 10 blogs about linked list:
http://juliachencoding.blogspot.ca/2016/05/hackerrank-linked-list-find-merge-point.html
http://juliachencoding.blogspot.ca/2016/05/hackerrank-insert-node-in-double-linked.html
Julia just marked all 13 linked list practice with label: linked list.
Use linked list in blog search to find all 13 of them.
Julia failed on one medium algorithm - recursive function in the contest. So, she likes to get some training on the skill.
A few reasons she failed:
1. Extra work - Recursive function involves building a string first.
2. Time consuming - use StringBuilder, backtracking
3. Failed to pass second test case; idea is not correct.
Previous work intensive on recursive function:
Last time Julia learned recursive work intensively through HackerRank Linked List:
started from May 8 to , over 10 blogs about linked list:
http://juliachencoding.blogspot.ca/2016/05/hackerrank-linked-list-find-merge-point.html
http://juliachencoding.blogspot.ca/2016/05/hackerrank-insert-node-in-double-linked.html
Julia just marked all 13 linked list practice with label: linked list.
Use linked list in blog search to find all 13 of them.
Tuesday, November 22, 2016
UVa online judge and a solution blog
Nov. 22, 2016
Plan to work on the UVa online judge and read the solution blog, and see if Julia enjoys the solution.
Blog reading:
UVa website
https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=36
Solution website: facebook tool engineer - ICPC winner in 2011 - 2012
http://www.questtosolve.com/browse.php
A few notes about how to start this blog with all solutions:
Julia worked on the HackerRank, and then, she followed one of player on twitter less than a week ago, who has an experience on ACM ICPC competition; and then, on Nov 22, 2016, Twitter sent an email about suggestion based on the connection: Wesley may @wjomlex, she followed, and then, she found the blog:
http://www.questtosolve.com/browse.php
Actionable items:
Work on 1 - 3 medium level algorithm by myself, and then, read the solutions. Tell at least 1 - 3 differences compared to HackerRank medium algorithm.
Plan to work on the UVa online judge and read the solution blog, and see if Julia enjoys the solution.
Blog reading:
UVa website
https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=36
Solution website: facebook tool engineer - ICPC winner in 2011 - 2012
http://www.questtosolve.com/browse.php
A few notes about how to start this blog with all solutions:
Julia worked on the HackerRank, and then, she followed one of player on twitter less than a week ago, who has an experience on ACM ICPC competition; and then, on Nov 22, 2016, Twitter sent an email about suggestion based on the connection: Wesley may @wjomlex, she followed, and then, she found the blog:
http://www.questtosolve.com/browse.php
Actionable items:
Work on 1 - 3 medium level algorithm by myself, and then, read the solutions. Tell at least 1 - 3 differences compared to HackerRank medium algorithm.
Monday, November 21, 2016
Minimum Cost - HackerRank woman codesprint #2 - Summary (Series 10 of 10)
Nov. 21, 2016
Here are the summary of HackerRank woman codesprint #2 minimum cost 10 blogs. The main goal is to improve performance, best performer can work on the algorithm in less than 10 minutes/ 30 lines of code. It takes a lot of insights to work smart and avoid time-consuming ideas.
Each blog serves one individual purpose for Julia's practice with an ordinary algorithm, medium level difficult, entry-level one.
Blog 1 - performance in the contest
http://juliachencoding.blogspot.ca/2016/11/womans-codesprint-2-minimum-loss-in.html
Blog 2 - study after the contest
http://juliachencoding.blogspot.ca/2016/11/womans-codesprint-2-minimum-loss-after.html
Blog 3 - Java TreeSet class - implementation in Java
http://juliachencoding.blogspot.ca/2016/11/java-treeset-study-minimum-loss.html
Blog 4 - C++ Set class - implementation in C++
http://juliachencoding.blogspot.ca/2016/11/c-14-set-class-study-minimum-loss.html
Blog 5 - C# SortedSet, SortedDictionary - implementation in C#
http://juliachencoding.blogspot.ca/2016/11/c-sorteddictionary-minimum-cost.html
Blog 6 - failed code study
http://juliachencoding.blogspot.ca/2016/11/minimum-cost-study-failed-code-partial.html
Blog 7 - Simplicity comparison, performance presentation
http://juliachencoding.blogspot.ca/2016/11/minimum-cost-comparison-of-simplicity-c.html
Blog 8 - Binary Search Tree algorithm, classical solution - Julia's favorite
http://juliachencoding.blogspot.ca/2016/11/binary-search-tree-algorithm-supports.html
Blog 9 - To be determined.
http://juliachencoding.blogspot.ca/2016/11/minimum-cost-hackerrank-woman.html
Blog 10 - inspiration by verse from tennis world champion - Roger Federal
When you're good at something, make that everything.
Here are the summary of HackerRank woman codesprint #2 minimum cost 10 blogs. The main goal is to improve performance, best performer can work on the algorithm in less than 10 minutes/ 30 lines of code. It takes a lot of insights to work smart and avoid time-consuming ideas.
Each blog serves one individual purpose for Julia's practice with an ordinary algorithm, medium level difficult, entry-level one.
Blog 1 - performance in the contest
http://juliachencoding.blogspot.ca/2016/11/womans-codesprint-2-minimum-loss-in.html
Blog 2 - study after the contest
http://juliachencoding.blogspot.ca/2016/11/womans-codesprint-2-minimum-loss-after.html
Blog 3 - Java TreeSet class - implementation in Java
http://juliachencoding.blogspot.ca/2016/11/java-treeset-study-minimum-loss.html
Blog 4 - C++ Set class - implementation in C++
http://juliachencoding.blogspot.ca/2016/11/c-14-set-class-study-minimum-loss.html
Blog 5 - C# SortedSet, SortedDictionary - implementation in C#
http://juliachencoding.blogspot.ca/2016/11/c-sorteddictionary-minimum-cost.html
Blog 6 - failed code study
http://juliachencoding.blogspot.ca/2016/11/minimum-cost-study-failed-code-partial.html
Blog 7 - Simplicity comparison, performance presentation
http://juliachencoding.blogspot.ca/2016/11/minimum-cost-comparison-of-simplicity-c.html
Blog 8 - Binary Search Tree algorithm, classical solution - Julia's favorite
http://juliachencoding.blogspot.ca/2016/11/binary-search-tree-algorithm-supports.html
Blog 9 - To be determined.
http://juliachencoding.blogspot.ca/2016/11/minimum-cost-hackerrank-woman.html
Blog 10 - inspiration by verse from tennis world champion - Roger Federal
When you're good at something, make that everything.
"When you're good at something, make that everything" - Roger Federer #tennis pic.twitter.com/9orryZK9w9— Tennis Coaching™️ (@tennisdothow) October 8, 2016
Minimum Cost - HackerRank woman codesprint #2 - Summary (Series 9 of 10)
Nov. 21, 2016
Plan to come out the idea for the slot - series of No. 9 of 10.
Roger Federal used to inspire Julia a lot with the verse. "Make your strength to everything."
Julia only survived on the contest of woman codesprint #2 with first one medium algorithm, from 3 medium, 2 hard algorithm, total 5 algorithm. So, she decided to make this medium algorithm to everything, blog the practice with a series of 10 blogs.
Ideas can be any one of them:
1. Find things to work on through studying submission, performance discussion, statistics of most popular solutions among C++, Java 8. 2.
2. Just warm up the algorithm with 1 -5 practices, different ideas.
Will come back soon. Julia's most favorite verse to motivate herself to serve better through blogging. Every effort makes different. Every blog counts to progress, no matter how small it is.
Life is like a game of tennis, the player who serves well seldom loses.
Plan to come out the idea for the slot - series of No. 9 of 10.
Roger Federal used to inspire Julia a lot with the verse. "Make your strength to everything."
Julia only survived on the contest of woman codesprint #2 with first one medium algorithm, from 3 medium, 2 hard algorithm, total 5 algorithm. So, she decided to make this medium algorithm to everything, blog the practice with a series of 10 blogs.
Ideas can be any one of them:
1. Find things to work on through studying submission, performance discussion, statistics of most popular solutions among C++, Java 8. 2.
2. Just warm up the algorithm with 1 -5 practices, different ideas.
Will come back soon. Julia's most favorite verse to motivate herself to serve better through blogging. Every effort makes different. Every blog counts to progress, no matter how small it is.
Life is like a game of tennis, the player who serves well seldom loses.
"Life is like a game of #tennis, the player who serves well seldom loses" #TennisQuotes pic.twitter.com/CICYQYeMfg— Tennis Coaching™️ (@tennisdothow) October 9, 2016
Sunday, November 20, 2016
HackerRank stone division - recursive design study (series 4 of 5)
Nov. 23, 2016
Introduction
It is time to get some training on recursive
function. Learn a few terms related to recursive function first, Julia can
describe what problems she had in the contest. She had problem to come out a
simple recursive function, after so many years hard working as a scholar and
full time programming experience.
She missed the important part to work on,
recursive step, build a recurrence formula.
C#
solution - copy the code from editorial notes: score 50 - maximum score,
pass all test cases
In the above C# solution, line 80:
ans = Math.Max(ans, 1 + ( (pile/runner) *
rec(runner) ) );
Study Recursive Function
Julia googles searched the recursive function, and then she found 3 things to work on. And then, she noticed that her study lacks depth of industry experience. She found an engineer on stackoverflow.com, and then she spent a few hours to read his blog. Great teaching about recursive.
Julia googles searched the recursive function, and then she found 3 things to work on. And then, she noticed that her study lacks depth of industry experience. She found an engineer on stackoverflow.com, and then she spent a few hours to read his blog. Great teaching about recursive.
Google Search: recursive function common mistakes
Choose some content to read:
Choose some content to read:
- university lecture notes - umd.edu
- IBM article
- lecture notes - MIT
- recursive function blogs
Here are the details.
1. university lecture notes - umd.edu:
Write down keywords:
c - core dump
c - compact code - recursive solution
h - How to think recursively?
s - stack space - recursive vs iterative
O(n) vs O(1)
stack size - several megabytes - 1000 recursive
calls
t - tail-recursive function
Google those keywords, and get more readings.
2. IBM article
Notes:
Inductive definition
inductively-defined
Bug source: state changes
Ideas to avoid bugs:
No variable does double-duty
Be certain that all variables hit the state they are
supposed to be in when the loop restarts.
One rule:
Assign a value to a variable only once and NEVER MODIFY IT!
1. Reusing a variable
2. Conditional modification of a variable
3. Loop variables
Base case proof.
Inductive step proof.
Two common mistakes:
1.
The base case is missing entirely. or the problem needs more than
one base case but not all the base cases are covered.
2.
The recursive step doesn't reduce to a smaller subproblem, so the
recursion doesn't converge.
base
cases
recursive
steps
decompose a recursive problem into recursive steps and base cases
when and how
to use helper methods in recursion
understand the
advantages and disadvantages of recursion vs. iteration
Structure of recursive implementations
- base case
- recursive step
A direct recursive implementation
Don't expose the helper method to your clients
Temporary state
Evolution of
the computation
Recurrence relation
Helper methods
Choose the
right recursive subproblem
4. Eric Lippert's blog about recursive function
More reading:
Recursion series:
Teach
how to think about recursion
Julia's notes
recursive way to think about a list emphasize the similarity of a fragment of
the list to the whole list.
recursively
define a list as either
1.
the empty list with zero items on it, or
2.
an item followed by a list
appear to be a circular definition, but it is really not. 'Spiral' definition
All recursive functions follow the same basic pattern:
Am
I in the base case? If so, return the easy solution.
Otherwise,
figure out some way to make the problem closer to the base case and solve that
problem.
bottom out - base case
A binary tree is either:
an
empty tree, or
a
value associated with two binary search trees, called the left and right child
trees.
inductive hypothesis -
1 million nodes - balanced tree - 20 recursive depth - 210 = 1024, so 1 million is around 220
"anonymous locals" -
callee's frame - caller's frame - current activation frame
the temporary variables are spelled out
each
recursion happens on its own line
Part three: build a dispatch engine
Follow up after 3 months
Feb 23, 2017
Because of this study, Julia looked into stackoverflow.com, and then she found the code review on stackexchange.com. She did great job to help herself, from a failure to solve a recursive function to study recursive function, know one person/ a blog/ code review site, she is no longer a lone coder. She asked a lot of questions and tried to answer a few questions. She tasted the success of solving problem with other's help.
Because of this study, Julia looked into stackoverflow.com, and then she found the code review on stackexchange.com. She did great job to help herself, from a failure to solve a recursive function to study recursive function, know one person/ a blog/ code review site, she is no longer a lone coder. She asked a lot of questions and tried to answer a few questions. She tasted the success of solving problem with other's help.
HackerRank stone division - after the contest (series 2 of 5)
Nov. 20, 2016
Introduction
HackerRank - woman codesprint #2 - stone division
Julia learned one algorithm a time after the contest. Every time she fails to solve an algorithm in the contest, it is her favorite learning time.
Spend 20 minutes to study Editorial Notes about the solution first.
1. Julia's C# solution followed the study:
After one hour study of the code converted in C#, Julia found out that she overcooked the solution, got too far to do the work instead of being lazy letting recursive function play the role.
First time again in a few month after she worked on linked list, she found out that she had to learn the tip again to fully take advantage of recursive function, give the confidence to allow recursive function to take care of business.
2. Let us learn the recursive again, let it do the beautiful work. And Julia take a break.
C# solution - copy the code from editorial notes: score 50 - maximum score, pass all test cases
https://gist.github.com/jianminchen/85980e8f52c701027fbf25a8f2293e96
Play with code, remove memorization, score 16/50, fail test case 11 and up
https://gist.github.com/jianminchen/de08d6a479e059b4238bec1d23ab6e12
Continue with a blog about recursion study.
Introduction
HackerRank - woman codesprint #2 - stone division
Julia learned one algorithm a time after the contest. Every time she fails to solve an algorithm in the contest, it is her favorite learning time.
Spend 20 minutes to study Editorial Notes about the solution first.
1. Julia's C# solution followed the study:
After one hour study of the code converted in C#, Julia found out that she overcooked the solution, got too far to do the work instead of being lazy letting recursive function play the role.
First time again in a few month after she worked on linked list, she found out that she had to learn the tip again to fully take advantage of recursive function, give the confidence to allow recursive function to take care of business.
2. Let us learn the recursive again, let it do the beautiful work. And Julia take a break.
C# solution - copy the code from editorial notes: score 50 - maximum score, pass all test cases
https://gist.github.com/jianminchen/85980e8f52c701027fbf25a8f2293e96
Play with code, remove memorization, score 16/50, fail test case 11 and up
https://gist.github.com/jianminchen/de08d6a479e059b4238bec1d23ab6e12
Continue with a blog about recursion study.
HackerRank - woman codesprint #2 - stone division - in the contest (series 1 of 5)
Nov. 20, 2016
Problem statement
Stone division
C# submission - need to continue to work on the solution
1. score 0, only pass the sample test case
2. second submission with more problems
Julia's idea to solve the problem:
She stopped on her third algorithm, worked so hard, over 5 hours, messing with recursive/ bugs with concatenating the string - her favorite test case: 2 3 4 6 8, n = 12
She tried so hard to work out on this test case:
2 3 4 6 8 12
2 T F T T T T - can divided by 2?
3
4
6
8
She worked on the backward to find all possible routes - for example, 12, 6, 3, or 12, 6, 2 etc.
Performance review:
It is hard to review the performance. Because Julia worked damn hard on this algorithm, she tried to push so hard and then she almost fell to sleep, she knew that she should cut the route she took; There is a lot of extra work she carelessly brought into the above submission.
Will continue later.
Problem statement
Stone division
C# submission - need to continue to work on the solution
1. score 0, only pass the sample test case
2. second submission with more problems
Julia's idea to solve the problem:
She stopped on her third algorithm, worked so hard, over 5 hours, messing with recursive/ bugs with concatenating the string - her favorite test case: 2 3 4 6 8, n = 12
She tried so hard to work out on this test case:
2 3 4 6 8 12
2 T F T T T T - can divided by 2?
3
4
6
8
She worked on the backward to find all possible routes - for example, 12, 6, 3, or 12, 6, 2 etc.
It is hard to review the performance. Because Julia worked damn hard on this algorithm, she tried to push so hard and then she almost fell to sleep, she knew that she should cut the route she took; There is a lot of extra work she carelessly brought into the above submission.
Will continue later.
Binary Search Tree - the algorithm supports the idea to solve "Minimum Cost" (series 8 of 10)
Nov. 20, 2016
Problem statement:
https://www.hackerrank.com/contests/womens-codesprint-2/challenges/minimum-loss
Julia spent a lot of time to try to get used to work on contest algorithms on HackerRank. She saw a lot of efforts she put in, but she was just the beginner of competitor programmer, maybe 10% compared to best talent in the world.
But, nothing can stop her to mentor herself to get through the stage, and become more confident on the competition. She started to know what to work on in the contest/ after the contest, understand most important things to do in order to get better.
One thing about the algorithm "Minimum Cost" is to handle the time complexity. Binary Search Tree is good enough algorithm to handle the scale of algorithm.
Look into the detail of description of problem:
next n years - the span of years - 200000, 0.2 million years,
n >= 2 and n <= 2 * 10^5, so n^2 will be around 4 * 10^10,
nlogn is best fit, since logn = 5, if 10 is base of log function.
No matter the solution is written in C++ or Java, most popular languages used in the top performers, they all chose to use binary search tree based on class, Java TreeSet is most popular one, and then, C++ Set which is also based on binary search tree.
Here is the just thoughts Julia likes to write a blog about the series, to make it to series of 8 of 10.
So, in order to understand the contest, competition better, as a former teaching assistant of computer science, Julia likes to study the solution of basic binary search tree, implemented in the way to return the minimum difference as a loss.
A lot of people stopped in the contest after this second algorithm. Julia felt the same way the difficulty. But she just likes to take one algorithm a time. Do not try to push herself too hard. She stopped on her third algorithm, worked so hard, over 5 hours, messing with recursive/ bugs with concatenating the string - her favorite test case: 2 3 4 6 8, n = 12
She tried so hard to work out on this test case:
2 3 4 6 8 12
2 T F T T T T - can divided by 2?
3
4
6
8
She worked on the backward to find all possible routes - for example, 12, 6, 3, or 12, 6, 2 etc.
Using Binary search - therefore, it is easy to find the minimum price, O(nlogn)
Maintain a binary search tree!
Study this C# solution using Binary search tree:
https://gist.github.com/jianminchen/c910f5d1f37309c70b489e6c75b0678c
Very classical solution using binary search tree, and very clever solution.
Memorize the solution. Warm up the solution sometimes in the future.
Problem statement:
https://www.hackerrank.com/contests/womens-codesprint-2/challenges/minimum-loss
Julia spent a lot of time to try to get used to work on contest algorithms on HackerRank. She saw a lot of efforts she put in, but she was just the beginner of competitor programmer, maybe 10% compared to best talent in the world.
But, nothing can stop her to mentor herself to get through the stage, and become more confident on the competition. She started to know what to work on in the contest/ after the contest, understand most important things to do in order to get better.
One thing about the algorithm "Minimum Cost" is to handle the time complexity. Binary Search Tree is good enough algorithm to handle the scale of algorithm.
Look into the detail of description of problem:
next n years - the span of years - 200000, 0.2 million years,
n >= 2 and n <= 2 * 10^5, so n^2 will be around 4 * 10^10,
nlogn is best fit, since logn = 5, if 10 is base of log function.
No matter the solution is written in C++ or Java, most popular languages used in the top performers, they all chose to use binary search tree based on class, Java TreeSet is most popular one, and then, C++ Set which is also based on binary search tree.
Here is the just thoughts Julia likes to write a blog about the series, to make it to series of 8 of 10.
So, in order to understand the contest, competition better, as a former teaching assistant of computer science, Julia likes to study the solution of basic binary search tree, implemented in the way to return the minimum difference as a loss.
A lot of people stopped in the contest after this second algorithm. Julia felt the same way the difficulty. But she just likes to take one algorithm a time. Do not try to push herself too hard. She stopped on her third algorithm, worked so hard, over 5 hours, messing with recursive/ bugs with concatenating the string - her favorite test case: 2 3 4 6 8, n = 12
She tried so hard to work out on this test case:
2 3 4 6 8 12
2 T F T T T T - can divided by 2?
3
4
6
8
She worked on the backward to find all possible routes - for example, 12, 6, 3, or 12, 6, 2 etc.
Using Binary search - therefore, it is easy to find the minimum price, O(nlogn)
Maintain a binary search tree!
Study this C# solution using Binary search tree:
https://gist.github.com/jianminchen/c910f5d1f37309c70b489e6c75b0678c
Very classical solution using binary search tree, and very clever solution.
Memorize the solution. Warm up the solution sometimes in the future.
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