leetcode54螺旋矩阵I

 输入：matrix = [[1,2,3],[4,5,6],[7,8,9]]
 输出：[1,2,3,6,9,8,7,4,5]

 class Solution {
 public:
     vector<int> spiralOrder(vector<vector<int>>& matrix) {
         if(matrix.empty())return{};
         int r=matrix[0].size()-1;
         int b=matrix.size()-1;
         int l=0,t=0;
         vector<int>res;
         while(1){
             for(int i=l;i<=r;i++)res.push_back(matrix[t][i]);//左到右
             if(++t>b)break;
             for(int i=t;i<=b;i++)res.push_back(matrix[i][r]);//上到下
             if(--r<l)break;
             for(int i=r;i>=l;i--)res.push_back(matrix[b][i]);//右到左
             if(--b<t)break;
             for(int i=b;i>=t;i--)res.push_back(matrix[i][l]);//下到上
             if(++l>r)break;
         }
         return res;
     }
 };