A collection of leetcode problems written in JavaScript or Python.
Over a course of 2 years, I recorded as many leetcode problems to help me in coding interviews and to win 5000 leetcode points for a t-shirt. I found that recording them here with my thought process was easier than reading leetcode explanations online.
Use these for coding interview prep. If you have questions, comments or suggestions feel free to post an issue in github!
- Go with the naive algorithm first! You want to gain some intuition and make sure you understand the problem fully.
- Then think about optimizations.
- Ask the interviewer if you are on the right path and ask for hints if you are stuck.
- Think about various inputs and outputs. Think about edge cases as well. Examples include - empty string, 0, false, weird punctuations for string problems, large inputs, small inputs, etc.
- Write up psuedocode if necessary to convey your idea to the interviewer. That way, the interviewer can verify your high level solution before implementation.
- After you finish coding the solution, test it out.
- Finally, examine the space and time complexity of your solution.
- Sliding Window
- Prefix/Suffix Sum, Prefix/Suffix Min or Max
- Interval Problems: use a stack and modify the last stack item if overlap, otherwise add it stack.
- Linked List: using a sentinel node.
- Linked List: slow and fast pointer. Have a fast pointer move by 2 while slow pointer goes by 1. OR if you want k difference, move fast pointer to k. Then move them both one by one.
- Backtracking
- Kadane's Algorithm
- Subsequences (Use DP with 2D matrix. Draw the 2D matrix to gain some intuition)
- 2Sum, 3Sum, 4Sum...if looking for indexes, you cannot sort. Otherwise, try sorting if it helps.
- Binary Search
- Subset Generation
- Permutation Generation
- Combination Generation
- Dynamic Programming via Top-Down vs Bottom-Up
Data Structures:
- Trie (you only ever need one trie when solving a problem)
- Heap (given index i, the parent node is
arr[(i - 1) // 2], the left node isarr[(i * 2) + 1]and the right node isarr[(i * 2) + 2]