Hash Table

Medium | Array, Hash Table, String

Medium | Array, Hash Table, Greedy, Sorting, Heap (Priority Queue), Counting

Easy | Array, Hash Table, Bit Manipulation, Sorting

Medium | Array, Hash Table, String, Trie

Medium | Hash Table, Tree, Depth-First Search, Binary Tree

Easy | Hash Table, Two Pointers, Tree, Depth-First Search, Breadth-First Search, Binary Search Tree, Binary Tree

Medium | Array, Hash Table, Greedy, Heap (Priority Queue)

Medium | Hash Table, String, Depth-First Search, Design, Trie

Medium | Array, Hash Table, Tree, Depth-First Search, Breadth-First Search

Hard | Array, Hash Table, String, Dynamic Programming, Backtracking, Bit Manipulation, Memoization, Bitmask