leetcode 1504. Count Submatrices With All Ones 统计全 1 子矩形

Problem: 1504. Count Submatrices With All Ones 统计全 1 子矩形计算矩阵的前缀和然后遍历所有的子矩阵看是否都是1也就是面积等于长乘以宽都是1的矩阵可以直接计算得到结果Codeclass Solution { public: int numSubmat(vectorvectorint mat) { int m mat.size(), n mat[0].size(); vectorvectorint prefix(m1, vectorint(n1, 0)); int sum 0, now, area, zero 0; for(int i 1; i m; i) { for(int j 1; j n; j) { prefix[i][j] prefix[i-1][j] prefix[i][j-1] - prefix[i-1][j-1] mat[i-1][j-1]; if(mat[i-1][j-1]0) zero; } } if(zero0) return (m1) * m * (n1) * n / 2 / 2; for(int i 0; i m; i) { for(int j 0; j n; j) { for(int k i1; k m; k) { for(int w j1; w n; w) { area (k - i) * (w - j); now prefix[k][w] - prefix[k][j] - prefix[i][w] prefix[i][j]; if(now area) sum; } } } } return sum; } };