5481：Desiderium

题目描述

There is a set of intervals, the size of this set is $n$.

If we select a subset of this set with equal probability, how many the expected length of intervals' union of this subset is?

We assume that the length of empty set's union is 0, and we want the answer multiply $2^n$ modulo $10^9 + 7$.

输入解释

The first line of the input is a integer $T$, meaning that there are $T$ test cases.

Every test cases begin with a integer $n$ ,which is size of set.

Then $n$ lines follow, each contain two integers $l , r$ describing a interval of $[l , r]$.

$1 \leq n \leq 100,000$.

$-1,000,000,000 \leq l \leq r \leq 1,000,000,000$.

输出解释

For every test case output the answer multiply $2^n$ modulo $10^9 + 7$.

输入样例

输出样例

1
7

提示

For the second sample, the excepted length is $\frac{0+2+2+3}{4}=\frac{7}{4}$.

来自杭电HDUOJ的附加信息

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该题目是Virtual Judge题目，来自杭电HDUOJ

题目来源 BestCoder Round #57 (div.2)

源链接： HDU-5481

最后修改于 2020-10-25T23:23:02+00:00 由爬虫自动更新

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通过率 --%

时间上限	内存上限
4000/2000MS(Java/Others)	65536/65536K(Java/Others)