题解 | 【模板】前缀和

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 1.读入数据
        int n = in.nextInt(), q = in.nextInt();
        int[] arr = new int[n+1];
        for (int i = 1; i <= n; i++) {
            arr[i] = in.nextInt();
        }

        // 2.预处理一个前缀和数组
        long[] dp = new  long[n + 1];   // 防止溢出
        for (int i = 1; i <= n; i++) {
            dp[i] = dp[i - 1] + arr[i];
        }

        // 3.使用前缀和数组
        while (q > 0) {
            int l = in.nextInt(), r = in.nextInt();
            System.out.println(dp[r] - dp[l - 1]);
            q--;
        }
    }
}