840. 矩阵中的幻方

840. 矩阵中的幻方

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题目链接：840. 矩阵中的幻方

代码如下：

class Solution {
public:
	int numMagicSquaresInside(vector<vector<int>>& grid) {
		int m = grid.size(),n = grid[0].size();
		int res = 0;

		for (int i = 0;i < m - 2;i++) {
			for (int j = 0;j < n-2;j++) {
				 if (grid[i + 1][j + 1] != 5) {
                    continue;
                }

				int mask = 0;
				int r_sum[3]{};
				int c_sum[3]{};
				for (int r = 0;r < 3;r++) {
					for (int c = 0;c < 3;c++) {
						int x = grid[i + r][j + c];
						mask |= 1 << x;
						r_sum[r] += x;
						c_sum[c] += x;
					}
				}

				if (mask == (1 << 10) - 2 &&
					r_sum[0] == 15 && r_sum[1] == 15 &&
					c_sum[0] == 15 && c_sum[1] == 15) {
					res++;
				}
			}
		}

		return res;
	}
};