leetcode Spiral Matrix I

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int> > &matrix) 
    {
        vector<int>v;
        int m=matrix.size();
        if(m==0)return v;
        int n=matrix[0].size();
        for(int i=0;2*i+1<=m&&2*i+1<=n;i++)
        {                
              for(int k=i;k<n-i;k++)
              {
               v.push_back(matrix[i][k]);
              }      
              for(int k=i+1;k<m-i-1;k++)
              {
                v.push_back(matrix[k][n-i-1]);
             }             
           if(m-1-i>=i+1)
           {
              for(int k=n-1-i;k>=i;k--)
              {
                v.push_back(matrix[m-1-i][k]);
              }
           }
           if(n-1-i>=i+1)
           {
               for(int k=m-2-i;k>=i+1;k--)
              {
                v.push_back(matrix[k][i]);
              }
           }        
        }
       return v;
    }
};