2019-08-19 螺旋矩阵

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++

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        if(matrix.empty() || matrix[0].empty()) return {};
        int x = matrix.size();
        int y = matrix[0].size();
        
        vector<int> res(x*y);
        vector<vector<int>> m(x, vector<int>(y, 0));
        vector<vector<int>> dirs{{0,1}, {1,0}, {0,-1}, {-1,0}};
        int r=0,c=0,k=0;
        for(int i=0;i<x*y;i++){
            res[i] = matrix[r][c];
            m[r][c] = 1;
            r+=dirs[k][0];
            c+=dirs[k][1];
            if(k == 0&&(c>=y || m[r][c] == 1)){
                c -= 1;
                r += 1;
                k = (k+1)%4;
            }
            if(k == 1&& (r>=x || m[r][c] == 1)){
                r -= 1;
                c -= 1;
                k = (k+1)%4;
            }
            if(k == 2&&(c<0 || m[r][c] == 1)){
                c += 1;
                r -= 1;
                k = (k+1)%4;
            }
            if(k == 3&&(r<0 || m[r][c] == 1)){
                r += 1;
                c += 1;
                k = (k+1)%4;
            }
            
        }
        return res;
    }
};