AcWing 796. 子矩阵的和

Posted 2022-02-09 MangataTS

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<bits/stdc++.h>
using namespace std;
#define ll long long
#define mod 1000000009
#define endl "\\n"
#define PII pair<int,int>
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 <= n; ++i) 
		for(int j = 1;j <= m; ++j) 
			cin>>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<<pre[x2][y2]-pre[x2][y1-1]-pre[x1-1][y2]+pre[x1-1][y1-1]<<endl;
	
	return 0;