5 articles
Traverse an m×n matrix in spiral order. Master the boundary-shrinking technique — maintain top, bottom, left, right walls and peel layer by layer. Covers edge cases, visual dry run, common bugs, Python & JavaScript solutions, and follow-ups like Spiral Matrix II.
Learn how to rotate an n×n matrix 90° clockwise in-place using the elegant transpose-then-reverse trick. Understand the math behind it, see the 4-cell direct rotation alternative, dry-run through a worked example, avoid the four most common mistakes, and get clean Python + JavaScript solutions.
LeetCode 240 Search a 2D Matrix II is a Google favourite that tests staircase elimination. We solve it in O(m + n) by walking from the top-right corner — beating the naive O(m * n) scan and the O(m * log n) per-row binary search.
LeetCode 378 (Medium) — a Google and Amazon staple. Solve k-th smallest in a row-and-column-sorted matrix with a min-heap k-way merge or binary search on the value range.
Solve LeetCode 85 Maximal Rectangle in O(m times n) by reducing each row to a histogram and applying the monotonic stack. A FAANG hard interview classic.