1.前缀和

import java.util.Scanner;
public class Main{
    public static void main(String []args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt(),q = sc.nextInt();
        int []a = new int[100010];
        int []b = new int[100010];
        for(int i=1;i<=n;i++){
            a[i] = sc.nextInt();
            b[i]=b[i-1]+a[i];
        }
        while(q-->0){
            int l = sc.nextInt(),r = sc.nextInt();   
            System.out.println(b[r]-b[l-1]);
        }
    }


}

2.二维前缀和

import java.util.Scanner;

public class Main{
    public static void main(String []args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt(),m =  sc.nextInt(),q = sc.nextInt();
        int [][]a = new int[n+1][m+1];
        int [][]s = new int[n+1][m+1];
        for(int i=1;i<=n;i++){
            for(int j=1;j<=m;j++){
                a[i][j] = sc.nextInt();
                s[i][j] = s[i-1][j] + s[i][j-1] - s[i-1][j-1]+a[i][j];
            }
        }

        while(q-->0){
            int x1 = sc.nextInt(),y1 = sc.nextInt(),x2 = sc.nextInt(),y2 = sc.nextInt();
            System.out.println(s[x2][y2]-s[x1-1][y2]-s[x2][y1-1]+s[x1-1][y1-1]);

        }
    }


}