LeetCode [48] Rotate Image

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]
]

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class Solution { public: void rotate(vector<vector<int>>& matrix) { int n = matrix.size(); for(int i = 0; i<=(n-1)/2; ++i){//layers from out-most to inner-most for(int j = i; j<n-1-i; ++j){ int top = matrix[i][j]; matrix[i][j] = matrix[n-1-j][i];//left -> top matrix[n-1-j][i] = matrix[n-1-i][n-1-j];//bottom -> left matrix[n-1-i][n-1-j] = matrix[j][n-1-i];//right -> bottom; matrix[j][n-1-i] = top;//top -> right; } } } };

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class Solution { public void rotate(int[][] matrix) { int n = matrix.length; int layers = n/2; for(int l = 0; l<layers; ++l){ int sz =n-2*l-1; for(int offset = 0; offset<sz; ++offset){ int tmp = matrix[l][l+offset]; //left to top matrix[l][l+offset] = matrix[n-1-l-offset][l]; //bottom to left matrix[n-1-l-offset][l] = matrix[n-1-l][n-1-l-offset]; //right to left; matrix[n-1-l][n-1-l-offset] = matrix[l+offset][n-1-l]; //top to right matrix[l+offset][n-1-l] = tmp; // print(matrix); } } } void print(int[][] matrix){ for(int[] r : matrix) System.out.println(Arrays.toString(r)); System.out.println("==========="); } }