Matrix Commands: Reverse / Swap / Rotate

Execute a sequence of in-place matrix commands — `reverseRow r`, `swap r1 r2`, `rotate` (90° clockwise) — and return the final matrix. Tests parsing discipline and 2-D index manipulation more than algorithmic depth. Requirements Input: an n x m integer matrix and a list of command strings. Supported commands: reverseRow r — reverse the elements of row index r. swap r1 r2 — swap rows r1 and r2. rotate — rotate the matrix 90 degrees clockwise. After a rotate, dimensions become m x n and subsequent row indices reference the rotated shape. Return the final matrix after all commands have been applied in order. Examples A 2 x 3 matrix [[1,2,3],[4,5,6]] after ["reverseRow 0", "rotate"] becomes [[4,3],[5,2],[6,1]]. Notes Two clean implementation paths: (a) maintain the matrix as a list-of-lists and recompute n, m after each rotate; (b) maintain logical row/column indices plus a rotation counter mod 4 and a row-reversal bitmap, applying the actual transformation lazily at the end. Path (a) is what to write under time pressure; path (b) is the follow-up answer if the interviewer asks about extending the command set to millions of operations. Command parsing is where most candidates lose time. Split on whitespace, then match on the first token before parsing the integers — do not try to regex the whole line. 90° clockwise rotation is M' = transpose(M) then reverse each row, or equivalently M'[i][j] = M[n-1-j][i]. Pick whichever is muscle memory; do not compose them in the wrong order under time pressure. After a rotate the row indices in any subsequent reverseRow r or swap r1 r2 refer to the rotated shape; failing to update the bounds is the typical bug. Preparation Build a unit-test harness with three matrices (square, wider-than-tall, taller-than-wide) and run all three through the same command sequence to catch dimension bugs. Memorise both rotation formulas and write them out from scratch in under a minute; this saves real time during the live attempt. Add rotateCCW and transpose as additional commands while practising — Capital One has been observed extending the prompt during the round when the candidate finishes early.