leetcode-----54. 螺旋矩阵

• 链接：https://leetcode-cn.com/problems/spiral-matrix/

代码

class Solution {
public:
    vector spiralOrder(vector>& matrix) {
        vector ans;
        int n = matrix.size();
        if (!n) return ans;
        int m = matrix[0].size();

        int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};
        vector> st(n, vector(m));

        for (int i = 0, x = 0, y = 0, d = 0; i < n * m; ++i) {
            ans.push_back(matrix[x][y]);
            st[x][y] = true;

            int a = x + dx[d], b = y + dy[d];
            if (a < 0 || a >= n || b < 0 || b >= m || st[a][b]) {
                d = (d + 1) % 4;
                a = x + dx[d], b = y + dy[d];
            }
            x = a, y = b;
        }
        return ans;
    }
};