leetcode-----59. 螺旋矩阵 II

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

代码

class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>> ans(n, vector<int>(n));
        int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};

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