array backtracking binary indexed tree binary search binary search tree binary tree bit manipulation bitmask brainteaser breadth-first search bucket sort combinatorics concurrency counting counting sort data stream depth-first search design divide and conquer doubly-linked list dynamic programming enumeration game theory geometry graph greedy hash function hash table heap (priority queue) interactive iterator linked list math matrix memoization minimum spanning tree monotonic queue monotonic stack number theory ordered set prefix sum probability and statistics queue quickselect radix sort randomized recursion reservoir sampling rolling hash segment tree shortest path simulation sliding window sorting stack string string matching topological sort tree trie two pointers union find