rotate-matrix.md

Rotate Matrix

Problem Description

You are given a n x n 2D matrix A representing an image. Rotate the image by 90 degrees (clockwise). You need to do this in place.

Note: If you end up using an additional array, you will only receive partial score.

Problem Constraints

1 <= n <= 1000

Input Format

First argument is a 2D matrix A of integers

Output Format

Return the 2D rotated matrix.

Example Input

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

Example Output

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

Example Explanation

Explanation 1:
After rotating the matrix by 90 degree:
1 goes to 2, 2 goes to 4
4 goes to 3, 3 goes to 1

Output

function rotateMatrix(A) {
    const n = A.length;

    // Step 1: Transpose the matrix
    for (let i = 0; i < n; i++) {
        for (let j = i; j < n; j++) {
            let temp = A[i][j];
            A[i][j] = A[j][i];
            A[j][i] = temp;
        }
    }

    // Step 2: Reverse each row
    for (let i = 0; i < n; i++) {
        A[i].reverse();
    }

    return A;
}

// Example usage:
let matrix = [
    [1, 2],
    [3, 4]
];

console.log(rotateMatrix(matrix));