题解 | 【模板】前缀和

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt(), q = scanner.nextInt();
        int[] arr = new int[n + 1];
        for (int i = 1; i < n + 1; i++) {
            arr[i] = scanner.nextInt();
        }
        long[] dp = new long[n + 1];
        for (int i = 1; i < n + 1; i++) {
            dp[i] = dp[i - 1] + arr[i];
        }

        while (q > 0) {
            int l = scanner.nextInt(), r = scanner.nextInt();
            System.out.println(dp[r] - dp[l - 1]);
            q--;
        }
        scanner.close();
    }
}