leetcode-54 螺旋矩阵

题目:

给定一个包含 m x n 个元素的矩阵（m 行, n 列），请按照顺时针螺旋顺序，返回矩阵中的所有元素。
示例 1:
输入:
[
[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]
]
输出: [1,2,3,6,9,8,7,4,5]
示例 2:
输入:
[
 [1, 2, 3, 4],
 [5, 6, 7, 8],
 [9,10,11,12]
]
输出: [1,2,3,4,8,12,11,10,9,5,6,7]

c++代码,解题思路同59题:

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        /*
        思路:
        同59 螺旋矩阵 2
        */
        vector<int>  res;
        if(matrix.empty()) return res;
        int up = 0;
        int down = matrix.size() - 1;  //col
        int left = 0;
        int right = matrix[0].size() - 1;  //row
        
        while(up <= down && left <= right){
            //left --> right
            for(int i = left; i <= right; i++){  
                res.push_back(matrix[up][i]);    //添加到res
            }
            //下一步要走的方向,依次类推
            if(++up > down) break;
            
            //up --> down
            for(int i = up; i <= down; i++){
                res.push_back(matrix[i][right]);
            }
            if(--right < left) break; 
            
            //right --> left
            for(int i = right; i >= left; i--){
                res.push_back(matrix[down][i]);
            }
            if(--down < up) break;  
            
            //down --> up
            for(int i = down; i >= up; i--){
                res.push_back(matrix[i][left]);
            }
            if(++left > right) break;
        }
        return res;
    }      
};