数组 - 旋转图像

/**
 * @param {number[][]} matrix
 * @return {void} Do not return anything, modify matrix in-place instead.
 */
var rotate = function(matrix) {
    var len = matrix.length;
    var loopNum = ~~(len / 2);

    for (var i = 0 ; i < loopNum ; i++) {
        for (var j = i ; j < len - i - 1 ; j++) {
            var exchangePoints = [
                [i, j],
                [j, len - i - 1],
                [len - i - 1, len - j - 1],
                [len - j - 1, i]
            ];
    
            var currentValue = matrix[exchangePoints[0][0]][exchangePoints[0][1]];
    
            exchangePoints.forEach(function(point, index) {
                var nextPoint = exchangePoints[(index + 1) % exchangePoints.length];
                var tmp = matrix[nextPoint[0]][nextPoint[1]];
                matrix[nextPoint[0]][nextPoint[1]] = currentValue;
                currentValue = tmp;
            });
        }
    }

    return matrix;
};

/**
 * @param {number[][]} matrix
 * @return {void} Do not return anything, modify matrix in-place instead.
 */

var rotate = function(matrix) {
    var i, j, temp;
    var len = matrix.length;
    for (i = 0; i < len - 1; i++) {
        for (j = i; i + j < len -1; j++) {
            temp = matrix[i][j];
            matrix[i][j] = matrix[len - 1 - j][i];
            matrix[len - 1 - j][i] = matrix[len - 1 - i][len - 1 - j];
            matrix[len - 1 - i][len - 1 - j] = matrix[j][len - 1 - i];
            matrix[j][len - 1 - i] = temp;
        }
    }
};