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Problem-Solving Patterns

How to think about a problem before you code it. · 14 topics

The call tree unfolds and folds (Fibonacci).

Dynamic Programming→

Fill a table, reuse subproblems (coin change).

Sliding Window→

A window slides across the array, no re-scan.

Backtracking→

Explore the decision tree, prune dead ends (N-Queens).

Two Pointers→

Converging pointers on a sorted array (pair sum).

Take the locally best choice each step (activity selection).

Kadane's Algorithm→

Maximum-sum contiguous subarray in one pass.

Sort 1..n in place by swapping each value home.

Merge Intervals→

Sort by start, fuse overlapping intervals.

Precompute totals; range sum in O(1).

Monotonic Stack→

Next greater element via a decreasing stack.

Fast & Slow Pointers→

Cycle detection (tortoise and hare).

Bit Manipulation→

Count set bits with n & (n−1).

Binary Search on Answer→

Search a monotonic answer space (integer √).