DSA Interview Roadmap

The backbone of every interview. Master frequency maps, prefix sums, and index tricks.

Eliminate nested loops by moving pointers inward or outward based on a condition.

Maintain a dynamic contiguous window to solve subarray/substring problems in O(n).

LIFO structure for matching, undo operations, and monotonic problems.

Halve the search space each iteration. Works on sorted arrays and answer-space problems.

Pointer manipulation, slow/fast runners, and reversal patterns.

Recursive DFS for most problems. BFS (level-order) for layer-by-layer questions.

O(log n) access to the min or max element. Essential for top-K and scheduling problems.

Build candidates incrementally and abandon ('backtrack') when a constraint is violated.

Model relationships. DFS for exploration; BFS for shortest unweighted paths.

Cache subproblem results to avoid redundant computation. Recognize overlapping subproblems.

Make the locally optimal choice at each step. Prove it leads to a global optimum.

Sort by start, then sweep. Merge overlaps, detect conflicts, insert cleanly.

XOR, shifts, and masks for elegant O(1) solutions to counting and parity problems.

Prefix tree for O(m) string search. Essential for autocomplete, spell-check, and word problems.

Dijkstra, Bellman-Ford, Prim's, Kruskal's. Weighted shortest paths and minimum spanning trees.