Rotate Image

Description

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]
]

Solution(javascript)

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