Code review: Hackerrank - count string

March 26, 2017

 Introduction 

Julia checked the blog stats and then she found out that last week there are over 70 60 views of the blog about Hackerrank: count string. So, she reviewed the 5 blogs related to the study of the algorithm, she quickly reformatted the blogs, and also plans to review the algorithm, and then post a question for code review.

Julia likes to learn something from Google, data driven. So, she makes decision what to review by blogger stats. She reviewed all five blogs related to count string algorithm quickly today, but she needs to reserve some time for a good review on algorithm itself.

Julia wrote 5 blogs in April 2016, this is the first blog. Julia failed to fix the issue to find those 5 blogs using search feature of blog, she worked on labels of those five blogs, somehow, it does not work.

Code review

HackerRank - String algorithm - Count Strings (I)

April 9, 2016

Problem statement


Category: Difficult problem

Spend 25 minutes to think about problem, and then will get into other people's submission, and see what should be learned.

10:30 am - 10:55 am

Spent 25 minutes to think about the problem.

Try to express the expression using binary tree, like 1 + 2 * 3 problem using a tree.

So, ab can be express as a tree:

operator .
/       \
a       b


 a|b
operator |
/           \
a            b

a*
put * as parent node, and a is left child of operator node *

(a*)5
put 5 as the parent node of operator *

Structure the input as tree structure, and then, define different class - concatOp, orOp, starOp

Read the expression from left to right, and then, put it into data structure like a stack, and then, parse it, store it in the binary tree.

April 10, 2016 2:32 pm 

This is a graph problem, and also, the NFA, DFA problem. Julia, you are lucky to review the problem. Spend some time in the short future to go over code, give yourself a graph coding experience.