#include "leetcode.h" class NumMatrix { public: vector> sum; NumMatrix(vector> &matrix) { int m = matrix.size(), n = matrix[0].size(); sum = vector>(m + 1, vector(n + 1)); for (int i = 1; i <= m; i++) for (int j = 1; j <= n; j++) sum[i][j] = sum[i - 1][j] + sum[i][j - 1] - sum[i - 1][j - 1] + matrix[i - 1][j - 1]; } int sumRegion(int row1, int col1, int row2, int col2) { row1++, col1++, row2++, col2++; return sum[row2][col2] - sum[row2][col1 - 1] - sum[row1 - 1][col2] + sum[row1 - 1][col1 - 1]; } }; int main() {}