| Sum + Subarray | Prefix Sum |
| Largest / Smallest / k-th in sorted | Heap / Quickselect |
| Arrange to Find Max / Min | Heap / Sort with Compare |
| Competing Choices / Select or Skip | Dynamic Programming |
| Remember Seen | Hashset / Hashmap |
| String Prefix | Trie |
| Pattern / Substring Matching | Rolling Hash / KMP |
| Repeated Sorting | Sorted List / Ordered Set |
| Binary Tree | Recursive Traverse / DFS |
| Count Steps in Graph / Matrix | BFS |
| Connectivity / Groups in Graph | Disjointed Set |
| Cycle Detection in Graph | Disjointed Set |
| Hash On or Off | Bitmask |
| DAG / Dependency / Causation | Topological Sort |
| Next Greater / Smaller | Mono Stack |
| In-place | Swap / Sorting / Two Pointers |
| Perm / Subset / Matrix Traverse / On or Off | Backtracking |
| Find First / Last Good Candidate | Binary Search |
Given k, find max / min | Binary Search |
| Find kth Element | Binary Search |
| Range Sum / Count in Rolling Sorted Array | Binary Index Tree / Segment Tree |
| Range Max / Min | Segment Tree |
| Balance / Last Few / Deletion | Stack |
| Count / Min / Max Subarray | Sliding Window |
| Count / Min / Max Subseq | Dynamic Programming |
| Subseq Pattern Matching | Dynamic Programming |
| Partition to k Subset / Knapsack | Dynamic Programming |
