AcWing 796. 子矩阵的和
原题链接
简单
作者:
小猫沾水
,
2024-03-05 15:02:00
,
所有人可见
,
阅读 22
算法
(前缀和) $O(n^m)$
C++ 代码
#include <bits/stdc++.h>
using namespace std;
const int N = 1005;
int n, m, q;
int a[N][N], s[N][N];
int main()
{
cin >> n >> m >> q;
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++)
cin >> a[i][j];
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++)
s[i][j] = s[i - 1][j] + s[i][j - 1] - s[i - 1][j - 1] + a[i][j]; // 矩阵前缀和公式
while (q--)
{
int x1, x2, y1, y2;
cin >> x1 >> y1 >> x2 >> y2;
int sum = s[x2][y2] - s[x2][y1 - 1] - s[x1 - 1][y2] + s[x1 - 1][y1 - 1]; // 定制矩阵和公式
cout << sum << "\n";
}
return 0;
}