Practice/Meta/Leetcode 48. Rotate Image

Leetcode 48. Rotate Image

CodingOptional

Problem

You are given a square 2D matrix (n × n) representing an image. Your task is to rotate the matrix by 90 degrees in the clockwise direction. The rotation must be performed in-place, meaning you cannot allocate another 2D matrix to solve this problem. You must modify the input matrix directly.

When rotating clockwise by 90 degrees:

• The first row becomes the last column
• The second row becomes the second-to-last column
• The last row becomes the first column

Requirements

1. Modify the matrix in-place without using extra space for another n × n matrix
2. Rotate the matrix exactly 90 degrees clockwise
3. The function should not return anything—it should modify the input matrix directly
4. Handle all valid matrix sizes from 1 × 1 up to the constraint limit

Constraints

• n == matrix.length == matrix[i].length
• 1 ≤ n ≤ 20
• -1000 ≤ matrix[i][j] ≤ 1000

Examples

Example 1:

Input: matrix = [[1,2,3],[4,5,6],[7,8,9]] Output: [[7,4,1],[8,5,2],[9,6,3]] Explanation: Original: After 90° rotation: 1 2 3 7 4 1 4 5 6 → 8 5 2 7 8 9 9 6 3

Example 2:

Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]] Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]] Explanation: Each element moves to its rotated position

Example 3:

Input: matrix = [[1]] Output: [[1]] Explanation: Single element remains in the same position