leetcode 54. 螺旋矩阵(Spiral Matrix)

题目描述：

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]

---

解法：

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        int x = 0, y = 0;
        bool right = true, down = false, left = false, up = false;
        
        int dx = 0, dy = 1;
        
        vector<int> res;
        int m = matrix.size();
        if(m == 0){
            return res;
        }else if(m == 1){
            return matrix[0];
        }
        int n = matrix[0].size();
        if(n == 0){
            return res;
        }else if(n == 1){
            for(vector<int> lst : matrix){
                res.push_back(lst[0]);
            }
            return res;
        }
        int idx = m*n;
        int min_x = 1, max_x = m-1;
        int min_y = 0, max_y = n-1;
        while(idx--){
            res.push_back(matrix[x][y]);
            x += dx;
            y += dy;
            if(right && y == max_y){
                right = false;
                down = true;
                dx = 1;
                dy = 0;
                max_y--;
            }else if(down && x == max_x){
                down = false;
                left = true;
                dx = 0;
                dy = -1;
                max_x--;
            }else if(left && y == min_y){
                left = false;
                up = true;
                dx = -1;
                dy = 0;
                min_y++;
            }else if(up && x == min_x){
                up = false;
                right = true;
                dx = 0;
                dy = 1;
                min_x++;
            }
        }
        return res;
    }
};