Spiral Matrix

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:
    void doit(int start,int row,int col,vector<int>& res,vector<vector<int> > matrix){
        
    }
    vector<int> spiralOrder(vector<vector<int> > &matrix) {
        vector<int> res;
        if(matrix.empty()) return res;
        int row=matrix.size()-1;
        int col=matrix[0].size()-1;
        if(row==-1||col==-1) return res;
        int start=0;
        int s=min(row,col);
        while(row>=0&&col>=0&&start<=s){
            if(res.size()==(matrix.size()*matrix[0].size())) break;
             if(row==start&&col==start) {res.push_back(matrix[start][start]);return res;}//只有一个数字
            if(row==start){//只有一行
                for (int i=start;i<=col;++i)
                    res.push_back(matrix[start][i]);
                break;
            }
            if(col==start){//只有一列
                for (int i=start;i<=row;++i)
                    res.push_back(matrix[i][start]);
                break;
            }
            for (int i=start;i<=col;++i) res.push_back(matrix[start][i]);
            for (int j=start+1;j<=row;++j) res.push_back(matrix[j][col]);
            for (int m=col-1;m>=start;--m) res.push_back(matrix[row][m]);
            for (int n=row-1;n>=start+1;--n) res.push_back(matrix[n][start]);
            ++start;
            --row;
            --col;
        }
        return res;
    }
};