Solution.ts

/**
 Do not return anything, modify matrix in-place instead.
 */
function rotate(matrix: number[][]): void {
    let n = matrix[0].length;
    for (let i = 0; i < Math.floor(n / 2); i++) {
        for (let j = 0; j < Math.floor((n + 1) / 2); j++) {
            let tmp = matrix[i][j];
            matrix[i][j] = matrix[n - 1 - j][i];
            matrix[n - 1 - j][i] = matrix[n - 1 - i][n - 1 - j];
            matrix[n - 1 - i][n - 1 - j] = matrix[j][n - 1 - i];
            matrix[j][n - 1 - i] = tmp;
        }
    }
}