59.螺旋矩阵-ii.cpp

/*
 * @lc app=leetcode.cn id=59 lang=cpp
 *
 * [59] 螺旋矩阵 II
 */

// @lc code=start
class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>> res(n, vector<int> (n));
        int dx[] = {0, 1, 0, -1} , dy[] = {1, 0, -1, 0};
        for (int i = 1, x = 0, y = 0, d = 0; i <= n * n; i++) {
            res[x][y] = i;
            int a = x + dx[d], b = y + dy[d];
            // 越界纠正
            if (a < 0 || a >= n || b < 0 || b >= n || res[a][b]) {
                d = (d + 1) % 4;
                a = x + dx[d], b = y + dy[d];
            }
            x = a, y = b;
        }
        return res;
    }
};
// @lc code=end