# 12001: 【原2001】Sum of Subsequences

### 题目描述

author: xjia 原OJ链接：https://acm.sjtu.edu.cn/OnlineJudge-old/problem/2001

## Description

Given a sequence of integers $$a_1, a_2, \dots, a_n$$, calculate the sum of the subsequences $$a_i + a_2 + \dots + a_j$$ with different pairs of $$i,j$$ specified.

## Input Format

Line 1: A positive integer $$n, 1 \leq n \leq 10000$$

Line 2: A sequence of $$n$$ integers $$a_1, a_2, \dots, a_n, \forall 1 \leq k \leq n, -10000 \leq a_k \leq 10000$$

Line 3: A positive integer $$m, 1 \leq m \leq 10000$$

Line 4 to $$m+3$$: Two positive integers $$i, j, 1 \leq i \leq j \leq n$$

## Output Format

Line 1 to $$m$$: An integer representing the sum of the subsequence with the specified pair of $$i, j$$

## Sample Input

5
1 3 4 2 5
2
2 4
1 3


## Sample Output

9
8


## Limits

Time limit: 1000ms, memory limit: 50000kb.

## satgo1546's solution

#include <cstdio>
using namespace std;

int a_[10010];
int *const a = &a_[4];

int main(int argc, char *argv[]) {
int n;
scanf("%d", &n);
for (int i = 0; i < n; i++) {
scanf("%d", &a[i]);
a[i] += a[i - 1];
}
scanf("%d", &argc);
while (argc--) {
int i, j;
scanf("%d%d", &i, &j);
printf("%d\n", a[j - 1] - a[i - 2]);
}
return 0;
}