Arrays & Hashing
Frequency counting, grouping, and lookups with hash maps and sets.
- 1.217. Contains Duplicate
- 2.242. Valid Anagram
- 3.1. Two Sum
- 4.49. Group Anagrams
- 5.347. Top K Frequent Elements
- 6.271. Encode and Decode Strings
- 7.238. Product of Array Except Self
- 8.36. Valid Sudoku
- 9.122. Best Time to Buy and Sell Stock II
- 10.128. Longest Consecutive Sequence
- 11.1929. Concatenation of Array
- 12.14. Longest Common Prefix
- 13.27. Remove Element
- 14.169. Majority Element
- 15.304. Range Sum Query 2D - Immutable
- 16.75. Sort Colors
- 17.560. Subarray Sum Equals K
- 18.705. Design HashSet
- 19.706. Design HashMap
- 20.912. Sort an Array
- 21.229. Majority Element II
- 22.41. First Missing Positive