Spiral Matrix

 1 public class Solution {
 2     public ArrayList<Integer> spiralOrder(int[][] matrix) {
 3         // IMPORTANT: Please reset any member data you declared, as
 4         // the same Solution instance will be reused for each test case.
 5         ArrayList<Integer> result = new ArrayList<Integer>();
 6         if(matrix == null||matrix.length == 0)
 7             return result;
 8         int m = matrix.length;
 9         int n = matrix[0].length;
10         spiralRecur(matrix, 0, result, m, n);
11         return result;
12     }
13     
14     private void spiralRecur(int[][] matrix, int layer, ArrayList<Integer> result, int m, int n){
15         int mlen = m - 2 * layer;
16         int nlen = n - 2 * layer;
17         
18         if(mlen <= 0 || nlen <= 0)
19             return;
20         if(mlen == 1 && nlen == 1)
21             result.add(matrix[layer][layer]);
22         else if(mlen == 1){
23             for(int i = 0; i < nlen; i++)
24             result.add(matrix[layer][layer + i]);
25         }
26         else if(nlen == 1){
27             for(int i = 0; i < mlen; i++)
28             result.add(matrix[layer + i][layer]);
29         }
30         else{
31             
32             for(int i = 0; i < nlen - 1; i++)
33                 result.add(matrix[layer][layer + i]);
34                 
35             for(int i = 0; i < mlen - 1; i++)
36                 result.add(matrix[layer + i][layer + nlen - 1]);
37                 
38             for(int i = 0; i < nlen - 1; i++)
39                 result.add(matrix[layer + mlen - 1][layer + nlen - 1 - i]);
40                 
41             for(int i = 0; i < mlen - 1; i++)
42                 result.add(matrix[layer + mlen - 1 - i][layer]);
43         }
44         spiralRecur(matrix, layer + 1, result, m ,n);
45     }
46 }