Acwing_795前缀和 【一维前缀和】 

题目：

代码： 

#include <bits/stdc++.h>
#define int long long
#define INF 0X3f3f3f3f
#define endl '\n'
using namespace std;
const int N = 100010;
int arr[N];int n,m;
int l,r;
signed main(){std::ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);cin>>n>>m;int sum[N];for(int i = 1; i <= n; i++){cin>>arr[i];sum[i]= sum[i-1] + arr[i];}while(m--){cin>>l>>r;cout<<sum[r]- sum[l-1]<<endl;}return 0;
}

【模板】二维前缀和 

例题

#include <bits/stdc++.h>
#define int long long
#define endl '\n'
#define INF 0x3f3f3f3f3f
using namespace std;const int N = 10010;
int arr[N][N],pre[N][N];
int n,c;signed main(){std::ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);int n,m;long long k;cin>>n>>m>>k;for(int i=1;i<=n;i++){for(int j=1;j<=m;j++){cin>>arr[i][j];pre[i][j]=pre[i-1][j]+pre[i][j-1]-pre[i-1][j-1]+arr[i][j];}}while(k--){int x1,y1,x2,y2;cin>>x1>>y1>>x2>>y2;cout<<pre[x2][y2]-pre[x1-1][y2]-pre[x2][y1-1]+pre[x1-1][y1-1]<<endl;}return 0;
}