18439二维前缀和

⭐️难度：中等

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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];

        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m; j++) {
                a[i][j] = scanner.nextInt();
            }
        }

        // 构造前缀和数组
        int[][] s = new int[1010][1010];
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m; j++) {
                s[i][j] = a[i][j] + s[i-1][j] + s[i][j-1] -s[i-1][j-1];
            }
        }

        // 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 sum = s[x2][y2] - s[x2][y1-1] - s[x1-1][y2] + s[x1-1][y1-1];
            System.out.println(sum);
        }
    }
}

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记住公式，然后直接套用就行