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48. Rotate Image

Medium

You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).

You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

Example 1:

Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]

Output: [[7,4,1],[8,5,2],[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]]

Example 3:

Input: matrix = [[1]]

Output: [[1]]

Example 4:

Input: matrix = [[1,2],[3,4]]

Output: [[3,1],[4,2]]

Constraints:

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

Solution

public class Solution {
    public void Rotate(int[][] matrix) {
        (int height, int width) = (matrix.Length, matrix[0].Length);
        for (int row = 0; row < height - 1; row++) {
            for (int col = row + 1; col < width; col++) {
                (matrix[col][row], matrix[row][col]) = (matrix[row][col], matrix[col][row]);
            }
        }
        for (int col = 0; col < width / 2; col++) {
            int oppositeCol = width - 1 - col;
            for (int row = 0; row < height; row++) {
                (matrix[row][col], matrix[row][oppositeCol]) = (matrix[row][oppositeCol], matrix[row][col]);
            }
        }
    }
}

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