rotate-image.js

// You are given an n x n 2D matrix representing an image.
//
// Rotate the image by 90 degrees (clockwise).
//
// Note:
//
// 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.
//
// Example 1:
//
//
// Given input matrix = 
// [
//   [1,2,3],
//   [4,5,6],
//   [7,8,9]
// ],
//
// rotate the input matrix in-place such that it becomes:
// [
//   [7,4,1],
//   [8,5,2],
//   [9,6,3]
// ]
//
//
// Example 2:
//
//
// Given input matrix =
// [
//   [ 5, 1, 9,11],
//   [ 2, 4, 8,10],
//   [13, 3, 6, 7],
//   [15,14,12,16]
// ], 
//
// rotate the input matrix in-place such that it becomes:
// [
//   [15,13, 2, 5],
//   [14, 3, 4, 1],
//   [12, 6, 8, 9],
//   [16, 7,10,11]
// ]
//
//


/**
 * @param {number[][]} matrix
 * @return {void} Do not return anything, modify matrix in-place instead.
 */
var rotate = function(matrix) {
    matrix = matrix.reverse()
    len = matrix.length
    for (var i = 1;i < len;++i) {
        for (var j = 0;j <i;++j) {
            var temp = matrix[i][j]
            matrix[i][j] = matrix[j][i]
            matrix[j][i] = temp
        }
    }
};