AcWing 796. 子矩阵的和

题目链接

https://www.acwing.com/problem/content/798/

思路

二维前缀和模板，在我的蓝桥集训之前缀和差分有讲到过：https://blog.csdn.net/m0_46201544/article/details/122371482

#include
using namespace std;
#define ll long long
#define mod 1000000009
#define endl "\n"
#define PII pair
ll ksm(ll a,ll b) {
	ll ans = 1;
	for(;b;b>>=1LL) {
		if(b & 1) ans = ans * a % mod;
		a = a * a % mod;
	}
	return ans;
}

ll lowbit(ll x){return -x & x;}

const int N = 2e3+10;
ll n,m,q,a[N][N],pre[N][N];

int main()
{
	cin>>n>>m>>q;
	for(int i = 1;i a[i][j];
			pre[i][j] = pre[i-1][j] + pre[i][j-1]-pre[i-1][j-1]+a[i][j];
		}
	}
	int x1,x2,y1,y2;
	while(q--) {
		cin>>x1>>y1>>x2>>y2;
		cout