x 48. Rotate Image

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In place: transpose + reverse

time: O(n x m)

space: O(1)

/**
 * @param {number[][]} matrix
 * @return {void} Do not return anything, modify matrix in-place instead.
 */
var rotate = function (matrix) {
    const n = matrix.length;
    for (let i = 0; i < n; i++) {
        for (let j = 0; j < i; j++) {
            transpose(matrix, i, j);
        }
    }

    for (let i = 0; i < n; i++) {
        for (let j = 0; j < Math.floor(n / 2); j++) {
            reverse(matrix, i, j);
        }
    }

};

function reverse(matrix, i, j) {
    const temp = matrix[i][j];
    matrix[i][j] = matrix[i][matrix.length - 1 - j];
    matrix[i][matrix.length - 1 - j] = temp;
}

function transpose(matrix, i, j) {
    const temp = matrix[i][j];
    matrix[i][j] = matrix[j][i];
    matrix[j][i] = temp;
}

time: O(n x m)

space: O(n x m)

/**
 * @param {number[][]} matrix
 * @return {void} Do not return anything, modify matrix in-place instead.
 */
var rotate = function(matrix) {
    const rotated = new Array(matrix.length).fill(null).map(v => new Array(matrix[0].length).fill(0));
    for (let i = 0; i < matrix.length; i++) {
        for (let j = 0; j < matrix[0].length; j++) {
            rotated[j][matrix.length - 1 - i] = matrix[i][j];
        }
    }

    for (let i = 0; i < matrix.length; i++) {
        for (let j = 0; j < matrix[0].length; j++) {
            matrix[i][j] = rotated[i][j];
        }
    }
};