DSA Patterns Roadmap

O(1) lookups for frequency counting and duplicate detection

Converge from both ends to find pairs in sorted data

Maintain a dynamic window over contiguous elements

Precompute cumulative sums for O(1) range queries

Halve the search space each step on sorted data

Sort to unlock greedy, two-pointer, and interval techniques

LIFO for bracket matching, undo, and DFS iteration

Solve problems by solving smaller versions of themselves

Pointer manipulation for reversal, merge, and partitioning

Detect cycles and find midpoints with two-speed traversal

Next greater/smaller element in O(n)

FIFO for BFS and sliding window max/min

Efficiently track top-K or merge-K sorted streams

Locally optimal choices that lead to global optimum

Visit every node systematically in hierarchical structures

Exploit sorted in-order property for O(log n) operations

Explore all candidates with pruning for constraint satisfaction

Explore connected nodes for islands, paths, and components

Sort and sweep to merge, insert, or find overlaps

Apply range updates in O(1) each, reconstruct with prefix sum

Cache overlapping subproblems — 1D, 2D, knapsack, LIS

Order nodes respecting dependency constraints in DAGs

Track and merge connected components in near O(1)

Fast prefix-based lookups for autocomplete and word search

Split, solve halves independently, combine results

XOR tricks, bitmask DP, and O(1) integer operations