1. Two Sum https://leetcode.com/problems/two-sum
128. Longest Consecutive Sequence https://leetcode.com/problems/longest-consecutive-sequence
290. Word Pattern https://leetcode.com/problems/word-pattern
519. Random Flip Matrix https://leetcode.com/problems/random-flip-matrix
138. Copy List with Random Pointer https://leetcode.com/problems/copy-list-with-random-pointer
133. Clone Graph https://leetcode.com/problems/clone-graph
242. Valid Anagram https://leetcode.com/problems/valid-anagram
49. Group Anagrams https://leetcode.com/problems/group-anagrams
387. First Unique Character in a String https://leetcode.com/problems/first-unique-character-in-a-string
169. Majority Element https://leetcode.com/problems/majority-element
389. Find the Difference https://leetcode.com/problems/find-the-difference
442. Find All Duplicates in an Array https://leetcode.com/problems/find-all-duplicates-in-an-array
448. Find All Numbers Disappeared in an Array https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array
Prerequisites
Before reading this article, you should first learn:
Hash tables are a commonly tested data structure in algorithm problems, mainly appearing in data structure design questions or in combination with arrays, strings, and other structures (such as the previous Prefix Sum Exercises). Here are some common hash table questions.
