Rotate Image

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.

LeetCode Problem - 48

class Solution {

    // Method to rotate the given n x n 2D matrix by 90 degrees clockwise
    public void rotate(int[][] matrix) {
        int n = matrix.length; // Length of the matrix

        // Step 1: Transpose the matrix
        // Swap elements at positions (i, j) with (j, i)
        for(int i = 0; i < n; i++){
            for(int j = i + 1; j < n; j++){
                int temp = matrix[i][j]; // Temporarily store the value at matrix[i][j]
                matrix[i][j] = matrix[j][i]; // Assign the value at matrix[j][i] to matrix[i][j]
                matrix[j][i] = temp; // Assign the temporarily stored value to matrix[j][i]
            }
        }

        // Step 2: Reverse each row
        // Swap elements in each row to reverse the row
        for(int i = 0; i < n; i++){
            for(int j = 0; j < n / 2; j++){
                int temp = matrix[i][j]; // Temporarily store the value at matrix[i][j]
                matrix[i][j] = matrix[i][n - j - 1]; // Assign the value at matrix[i][n - j - 1] to matrix[i][j]
                matrix[i][n - j - 1] = temp; // Assign the temporarily stored value to matrix[i][n - j - 1]
            }
        }
    }
}