DSA · Matrix · #155
Rotate Image
Module 63 · difficulty 3/5·⏱ 30:00starts on first keystroke
Given an `n x n` 2D `matrix` representing an image, rotate the image by **90 degrees clockwise**, **in place**. You must modify the input matrix directly — do **not** allocate another 2D matrix to perform the rotation. The function returns nothing (`undefined`); the rotation must be reflected in the passed-in `matrix`. Implement `rotate(matrix)`.
Examples
matrix = [[1,2,3],[4,5,6],[7,8,9]]→[[7,4,1],[8,5,2],[9,6,3]]— The top row 1,2,3 becomes the right column.matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]→[[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]matrix = [[1]]→[[1]]— A single element is unchanged.
Constraints
- · n == matrix.length == matrix[i].length
- · 1 <= n <= 20
- · -1000 <= matrix[i][j] <= 1000
- · Rotation must be performed in place with O(1) extra space.
Session phases
A · Clarify
B · Approach
C · Complexity
D · Edges
E · Code
F · Tradeoff
G · Score
Phase A — Clarify
Ask questions about input bounds, types, and edge constraints.
Ask the coach clarifying questions about the problem.
When you've covered this phase, advance to the next.