59. Spiral Matrix II

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题目

https://leetcode.com/problems/spiral-matrix-ii/description/

-w951

想法

其实就是考虑一些边界值，考虑的好，就写起来很简洁

还有四个方向的变化，怎么统一起来，一点小trick

答案

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class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>> res(n, vector<int>(n, 0));
        int i = 0, j = 0;
        vector<int> h{1, 0, -1, 0};
        vector<int> v{0, 1, 0, -1};
        int d = 0;
        res[i][j] = 1;
        for (int k = 2; k <= n * n; k++) {
            int ti = i + v[d];
            int tj = j + h[d];
            if (!(ti >= 0 && ti < n && tj >= 0 && tj < n && res[ti][tj] == 0)) {
                d = (d + 1) % 4;
            }
            i = i + v[d];
            j = j + h[d];
            res[i][j] = k;
        }
        return res;
    }
};