matrix

Rotating a matrix in place probes index manipulation and the transpose-then-reverse trick. What interviewers watch for: splitting the rotation into two simple passes instead of juggling four-way swaps. Here is the answer.

Spiral traversal probes careful boundary management more than algorithmic insight. Interviewers look for shrinking four boundaries layer by layer without double-visiting a row or column. The answer follows.

A row- and column-sorted matrix rewards a single insight: begin at a corner and drop a whole row or column each step. That converts an O(m*n) scan into O(m+n), and which corner you pick is not arbitrary.