Rotate Image leetcode java

題目：

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

Rotate the image by 90 degrees (clockwise).

Follow up:
Could you do this in-place?

 

題解：

這道題就是考察很直白的旋轉坐標。要in place的。畫個圖自己算算就出來了。

代碼如下：

 

 
           1   
          /* 
             public void rotate(int[][] matrix) {
 
           2  
                  int m = matrix.length;
 
           3  
                  int n = matrix[0].length;
 
           4  
                  
 
           5  
                  int[][] result = new int[m][n];
 
           6  
                  
 
           7  
                  for(int i = 0; i<m; i++){
 
           8  
                      for(int j = 0; j<n; j++){
 
           9  
                          result[j][m-1-i] = matrix[i][j];
 
          10  
                      }
 
          11  
                  }
 
          12  
                  
 
          13  
                  for(int i=0;i<m;i++){
 
          14  
                      for(int j=0; j<n; j++){
 
          15  
                           matrix[i][j] = result[i][j];
 
          16  
                      }
 
          17  
                  }
 
          18  
              }
 
          19  
               
          */ 
          
 
          20      
          
 
          21      
          // 
          in place 
          
 
          22  
               
          public  
          void rotate( 
          int[][] matrix) { 
          
 
          23      
          int n = matrix.length; 
          
 
          24      
          for ( 
          int i = 0; i < n / 2; i++) { 
          
 
          25          
          for ( 
          int j = 0; j < Math.ceil((( 
          double) n) / 2.); j++) { 
          
 
          26              
          int temp = matrix[i][j]; 
          
 
          27             matrix[i][j] = matrix[n-1-j][i]; 
          
 
          28             matrix[n-1-j][i] = matrix[n-1-i][n-1-j]; 
          
 
          29             matrix[n-1-i][n-1-j] = matrix[j][n-1-i]; 
          
 
          30             matrix[j][n-1-i] = temp; 
          
 
          31         } 
          
 
          32     }