AcWing 796. 子矩阵的和

解题思路

样例

1 7 2 4

3 6 2 8

2 1 2 3
求任意子矩阵的和

二维前缀和公式

相关代码

import java.util.Scanner;

public class Main {


    public static void main(String[] args){
        //二维子矩阵的元素和
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int m = scanner.nextInt();
        int q = scanner.nextInt();
        int a[][] = new int[n+1][m+1];
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                a[i][j] = scanner.nextInt();

        //进行前缀和预处理
        int s[][] = new int[n+1][m+1];
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                s[i][j]=s[i][j-1]+s[i-1][j]-s[i-1][j-1]+a[i][j];


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