LeetCode Solutions and Explanations

Here is a list of LeetCode problems solved by Goodtecher. Goodtecher will keep updating solutions and explains to LeetCode problems. You can also watch GoodTecher LeetCode Video Tutorial on Youtube.

LeetCode Problems Table

#	Title	Category	Difficulty	Frequency
1	Two Sum	Two Pointers	Easy	★★★★★
2	Add Two Numbers	Linked List	Medium	★★★★
3	Longest Substring Without Repeating Characters	Two Pointers	Medium	★★★★
4	Median of Two Sorted Arrays	Array	Hard	★★★
5	Longest Palindromic Substring	Dynamic Programming	Medium	★★★★
6	ZigZag Conversion	Math	Medium	★
7	Reverse Integer	Math	Easy	★★★★
8	String to Integer (atoi)	String	Medium	★★
9	Palindrome Number	Math	Easy	★★★★
11	Container With Most Water	Two Pointers	Medium	★★
12	Integer to Roman	String	Medium	★
13	Roman to Integer	String	Easy	★
14	Longest Common Prefix	String	Easy	★★★
15	3Sum	Two Pointers	Medium	★★★
16	3Sum Closest	Two Pointers	Medium	★★★
17	Letter Combinations of a Phone Number	Depth First Search	Medium	★★★
18	4Sum	Two Pointers	Medium	★★
19	Remove Nth Node From End of List	Linked List	Medium	★★★
20	Valid Parentheses	Stack	Easy	★★★★
21	Merge Two Sorted Lists	Linked List	Easy	★★★
26	Remove Duplicates from Sorted Array	Two Pointers	Easy	★★
28	Implement strStr()	String	Easy	★★
34	Search for a Range	Binary Search	Medium	★★
35	Search Insert Position	Binary Search	Easy	★★
39	Combination Sum	Depth First Search	Medium	★★★★
40	Combination Sum II	Depth First Search	Medium	★★★
42	Trapping Rain Water	Two Pointers	Hard	★★★
62	Unique Paths	Dynamic Programming	Medium	★★★
63	Unique Paths II	Dynamic Programming	Medium	★★
69	Sqrt(x)	Binary Search	Easy	★★★
70	Climbing Stairs	Dynamic Programming	Easy	★★★
78	Subsets	Depth First Search	Medium	★★★★
90	Subsets II	Depth First Search	Medium	★★
100	Same Tree	Binary Tree	Easy	★★★
101	Symmetric Tree	Binary Tree	Easy	★★★
102	Binary Tree Level Order Traversal	Binary Tree	Medium	★★★★
104	Maximum Depth of Binary Tree	Binary Tree	Easy	★★★
110	Balanced Binary Tree	Binary Tree	Easy	★★★
111	Minimum Depth of Binary Tree	Binary Tree	Easy	★★★
121	Best Time to Buy and Sell Stock	Array	Easy	★★
122	Best Time to Buy and Sell Stock II	Array	Easy	★★
138	Copy List with Random Pointer	Linked List	Medium	★★
139	Word Break	Dynamic Programming	Medium	★★★★
144	Binary Tree Preorder Traversal	Binary Tree	Easy	★★
155	Min Stack	Stack	Easy	★★★
278	First Bad Version	Binary Search	Easy	★★
412	Fizz Buzz	Math	Easy	★★★
547	Friend Circles	Union Find	Medium	★★★

35 Thoughts to “LeetCode Solutions and Explanations”

millie says:

August 18, 2018 at 7:35 am

Hey goodtecher,

Can you add a column for https://www.interviewbit.com/ and add answers ??

1. GoodTecher says:
  
  August 19, 2018 at 11:22 pm
  
  Thanks for the suggestion. I will take a look at the website 🙂
  
Aneetha says:

July 31, 2018 at 11:46 pm

Thank You for the tutorials and videos. Your explanation is amazing. Looking forward for more videos.

1. GoodTecher says:
  
  August 4, 2018 at 10:31 pm
  
  Thank you Aneetha! Will keep making progress : )
  
lawrence says:

July 10, 2018 at 3:11 pm

Hi goodtecher,
any plans on this question:
https://leetcode.com/problems/largest-rectangle-in-histogram/description/

I would like to see how stack could be used as well as if dp is possible with this.

1. GoodTecher says:
  
  July 28, 2018 at 3:00 pm
  
  Thank you Lawrence for your question. I will take a look at the question.
  
2. GoodTecher says:
  
  August 19, 2018 at 11:22 pm
  
  Hi lawrence, the tutorial about this problem is uploaded. 🙂
  https://www.youtube.com/watch?v=gUVmeVjHZY4&list=PLV8H0QrJHjOmhbwotwt3Sy8qlfzqGhVW-&t=176s&index=33
  
Em says:

February 16, 2018 at 11:05 am

Happy New Year, Good Techer!

1. GoodTecher says:
  
  February 17, 2018 at 2:58 pm
  
  Thank you Em! Happy Lunar New Year!
  
Elvin says:

February 7, 2018 at 2:32 am

Thank you for your tutorials and youtube videos

1. GoodTecher says:
  
  February 10, 2018 at 11:30 am
  
  Thank you Elvin ! : )

LeetCode Problems Table

35 Thoughts to “LeetCode Solutions and Explanations”

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