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QOJ

Time Limit: 4 s Memory Limit: 512 MB Total points: 100

#5186. 本质不同逆序对

统计

题目描述

给定一个长为 $n$ 的序列 $a$。

有 $m$ 次询问,每次询问给定一个区间 $[l,r]$,求 $|\{(a_i,a_j) : l\le i < j\le r \wedge a_i>a_j\}|$。

$1\le n\le 10^5$,$1\le m\le 5\times 10^5$。

输入格式

第一行一个正整数 $n$。

第二行 $n$ 个正整数,其中第 $i$ 个数 $a_i$ 表示序列第 $i$ 个位置的值,保证 $1\leq a_i \leq n$。

第三行一个正整数 $m$。

之后 $m$ 行,每行用两个空格隔开的正整数,分别表示 $l,r$,表示一次询问,保证 $1\leq l\le r \leq n$。

输出格式

输出 $m$ 行,第 $i$ 行输出一行一个整数,表示第 $i$ 次询问的答案。

样例数据

样例 1 输入

5
2 1 3 2 1
4
2 4
1 5
3 5
2 2

样例 1 输出

1
3
3
0

样例 1 解释

对于第一次询问,集合为 $\{(3,1)\}$。

对于第二次与第三次询问,集合为 $\{(2,1),(3,1),(3,2)\}$。

对于第四次询问,集合为空集。

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