题解 | #【模板】二维前缀和#
【模板】二维前缀和
https://www.nowcoder.com/practice/99eb8040d116414ea3296467ce81cbbc
先求矩阵和
#include <iostream>
#include <vector>
using namespace std;
int main() {
int n, m, q;
cin >> n >> m >> q;
vector<vector<long long>> A(n + 1, vector<long long>(m + 1));
A[0][0] = 0;
for(int i = 0; i <= n; ++i) {
A[i][0] = 0;
}
for(int j = 0; j <= m; ++j)
A[0][j] = 0;
for(int i = 1; i <= n; ++i) {
for(int j = 1; j <= m; ++j) {
long long num;
cin >> num;
// 先求矩阵和
A[i][j] += A[i - 1][j] + A[i][j - 1] - A[i - 1][j - 1] + num;
// cout << A[i][j] << " ";
}
}
while(q--) {
int x1, y1, x2, y2;
cin >> x1 >> y1 >> x2 >> y2;
long long ans = A[x2][y2] - A[x2][y1 - 1] - A[x1 - 1][y2] + A[x1 - 1][y1 - 1];
cout << ans << endl;
}
return 0;
}
