题解 | 【模板】静态区间和（前缀和）-Java

import java.util.Scanner;

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

        // 读取数组长度和查询次数
        int n = scanner.nextInt();
        int q = scanner.nextInt();

        // 读取数组元素
        long[] a = new long[n + 1];  // 使用1-based索引
        for (int i = 1; i <= n; i++) {
            a[i] = scanner.nextLong();
        }

        // 计算前缀和
        long[] prefixSum = new long[n + 1];
        for (int i = 1; i <= n; i++) {
            prefixSum[i] = prefixSum[i - 1] + a[i];
        }

        // 处理每个查询
        for (int i = 0; i < q; i++) {
            int l = scanner.nextInt();
            int r = scanner.nextInt();
            // 区间和 = 前r项和 - 前(l-1)项和
            System.out.println(prefixSum[r] - prefixSum[l - 1]);
        }

        scanner.close();
    }
}