Spiral Matrix I

来源：Leetcode

原帖：http://oj.leetcode.com/problems/spiral-matrix/

题目：
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].

代码：

 class Solution {  
 public:  
   vector<int> spiralOrder(vector<vector<int> > &matrix) {  
     if (matrix.empty() || matrix[0].empty()) return {};  
     vector<int> res;  
     int imin = 0, imax = matrix.size() - 1;  // row  
     int jmin = 0, jmax = matrix[0].size() - 1; // col  
     while (1) {  
       for (int j = jmin; j <= jmax; ++j) res.push_back(matrix[imin][j]);  
       if (++imin > imax) break;   
   
       for (int i = imin; i <= imax; ++i) res.push_back(matrix[i][jmax]);          
       if (jmin > --jmax) break;  
   
       for (int j = jmax; j >= jmin; --j) res.push_back(matrix[imax][j]);          
       if (imin > --imax) break;  
   
       for (int i = imax; i >= imin; --i) res.push_back(matrix[i][jmin]);          
       if (++jmin > jmax) break;  
     }  
     return res;  
   }  
 };