LeetCode Spiral Matrix

 1 public class Solution {
 2     public List<Integer> spiralOrder(int[][] matrix) {
 3         List<Integer> res = new ArrayList<Integer>();
 4         if(matrix == null || matrix.length == 0 || matrix[0].length == 0){
 5             return res;
 6         }
 7         int m = matrix.length;
 8         int n = matrix[0].length;
 9         int x = 0;
10         int y = 0;
11         
12         while(m>0 && n>0){
13             //There is only one row
14             if(m == 1){
15                 for(int i = 0; i<n; i++){
16                     res.add(matrix[x][y++]);
17                 }
18                 break;
19             }
20             //There is only one column
21             else if(n == 1){
22                 for(int i = 0; i<m; i++){
23                     res.add(matrix[x++][y]);
24                 }
25                 break;
26             }
27             
28             //Below is for circle
29             //Top, move right
30             for(int i = 0; i<n-1; i++){
31                 res.add(matrix[x][y++]);
32             }
33             
34             //Right, move down
35             for(int i = 0; i<m-1; i++){
36                 res.add(matrix[x++][y]);
37             }
38             
39             //Bottom, move left
40             for(int i = 0; i<n-1; i++){
41                 res.add(matrix[x][y--]);
42             }
43             
44             //Left, move up
45             for(int i = 0; i<m-1; i++){
46                 res.add(matrix[x--][y]);
47             }
48             
49             x++;
50             y++;
51             m-=2;
52             n-=2;
53         }
54         return res;
55     }
56 }