Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

For example,
Given the following matrix:

[
 [ 1, 2, 3 ],
 [ 4, 5, 6 ],
 [ 7, 8, 9 ]
]

You should return [1,2,3,6,9,8,7,4,5].

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 1 public class Solution {
 2     public List<Integer> spiralOrder(int[][] matrix) {
 3         List<Integer> ans = new ArrayList<Integer>();
 4         if(matrix == null || matrix.length == 0 || matrix[0].length == 0) return ans;
 5         int startx = 0,starty = 0,endx = matrix[0].length-1,endy = matrix.length-1;
 6
 7         while(startx <= endx && starty <= endy){
 8             for(int i = startx;i<=endx && starty <= endy;i++){// 该题这里需要判断下 starty endy 的边界，不然容易重复加入list
 9                 ans.add(matrix[starty][i]);
10             }
11             starty++;
12
13             for(int i = starty;i<=endy && startx <= endx;i++){
14                  ans.add(matrix[i][endx]);
15             }
16             endx--;
17
18             for(int i = endx;i>=startx && starty <= endy;i--){
19                 ans.add(matrix[endy][i]);
20             }
21             endy--;
22
23             for(int i = endy;i>=starty && startx <= endx;i--){
24                 ans.add(matrix[i][startx]);
25             }
26             startx++;
27         }
28         return ans;
29     }
30 }

对比59

Spiral Matrix II java solutions

http://www.cnblogs.com/guoguolan/p/5620000.html