18440二维差分

18440二维差分

⭐️难度：中等
📖

📚

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int n = scanner.nextInt();
        int m = scanner.nextInt();
        int q = scanner.nextInt();
        int[][] a = new int[1010][1010];
        int[][] b = new int[1010][1010];

        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m; j++) {
                a[i][j] = scanner.nextInt();
                b[i][j] = a[i][j] + a[i-1][j-1] - a[i-1][j] - a[i][j-1]; // 求差分数组
            }
        }

        // 子矩阵求和
        for (int i = 0; i < q; i++) {
            int x1 = scanner.nextInt();
            int y1 = scanner.nextInt();
            int x2 = scanner.nextInt();
            int y2 = scanner.nextInt();
            int d = scanner.nextInt();
            
            b[x1][y1] += d;
            b[x1][y2+1] -= d;
            b[x2+1][y1] -= d;
            b[x2+1][y2+1] += d;
        }
        
        // 差分数组求前缀和还原原数组
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m; j++) {
                b[i][j] = b[i][j] - b[i-1][j-1] + b[i-1][j] + b[i][j-1]; // 直接用b数组求前缀和
                System.out.print(b[i][j]+" ");
            }
            System.out.println();
        }
    }
}

🐱笔记

背公式，用公式。