前缀和模板

一维前缀和模板

#include 

using namespace std;
const int N = 1e5 + 10;
int a[N];

int main(){
    int n, m;
    cin >> n >> m;
    
    for (int i = 1; i <= n; i ++){
        cin >> a[i];
        a[i] = a[i - 1] + a[i];
    } 
    
    // 计算输出
    while(m --){
        int l, r;
        cin >> l >> r;
        
        cout << a[r] - a[l - 1] << endl;
    }
    return 0;
}

二维前缀和模板

#include 

using namespace std;

const int N = 1010;
int a[N][N];

int main(){
    int n, m, q;
    cin >> n >> m >> q;
    
    // 读入矩阵
    for(int i = 1; i <= n; i ++){
        for (int j = 1; j <= m; j ++){
            cin >> a[i][j];
            a[i][j] = a[i][j-1] + a[i-1][j] - a[i-1][j-1] + a[i][j];
        }
    }
    

    
    // 输出子矩阵和
    while(q --){
        int x1, y1, x2, y2;
        cin >> x1 >> y1 >> x2 >> y2;
        
        cout << a[x2][y2] - a[x2][y1-1] - a[x1-1][y2] + a[x1-1][y1-1] << endl;
    }
    
    return 0;
}