48.Rotate Image

[niuworld]

Question:

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Solution:

思路：将正方形分解为一个套一个的正方形，从矩阵的最外层（一个正方形），开始变换，一直循环到到中间的四个元素组成的正方形。

class Solution {
public:
    void rotate(vector<vector<int>>& matrix) {
        vector<vector<int>> result;
        int n = matrix.size();
        int i , j ;
        if(n == 0 ) return ;
        if(n == 1 ) return ;
        for(i = 0 ; i < n/2; i++)
          for( j = i ; j < n - i - 1; j++){
              int temp = matrix[i][j];
              matrix[i][j] =  matrix[n-1-j][i];
              matrix[n-1-j][i] = matrix[n-1-i][n-1-j];
              matrix[n-1-i][n-1-j] = matrix[j][n-1-i];
              matrix[j][n-1-i] = temp;
          }
    }
};