matrix

Rotating a matrix in place tests index manipulation and the transpose-then-reverse trick. The signal is decomposing the rotation into two simple passes rather than juggling four-way swaps. Here is the answer.

Spiral traversal tests careful boundary management more than algorithmic insight. The signal is shrinking four boundaries layer by layer without double-visiting a row or column. Here is the answer.

A row- and column-sorted matrix rewards one observation: start from a corner and kill an entire row or column each step. That turns an O(m*n) scan into O(m+n), and the choice of corner is not arbitrary.