VK Cup 2016 - Round 3
E
Bear and Destroying Subtrees
Codeforces
2700
原题
← DF →
翻译中…

Limak is a little grizzly bear. He will once attack Deerland but now he can only destroy trees in role-playing games. Limak starts with a tree with one vertex. The only vertex has index $1$ and is a root of the tree.

翻译中…

Sometimes, a game chooses a subtree and allows Limak to attack it. When a subtree is attacked then each of its edges is destroyed with probability image, independently of other edges. Then, Limak gets the penalty — an integer equal to the height of the subtree after the attack. The height is defined as the maximum number of edges on the path between the root of the subtree and any vertex in the subtree.

翻译中…

You must handle queries of two types.

翻译中…
  • 1 v denotes a query of the first type. A new vertex appears and its parent is $*v*$. A new vertex has the next available index (so, new vertices will be numbered $2, 3, ...$).
  • 2 v denotes a query of the second type. For a moment let's assume that the game allows Limak to attack a subtree rooted in $*v*$. Then, what would be the expected value of the penalty Limak gets after the attack?
翻译中…

In a query of the second type, Limak doesn't actually attack the subtree and thus the query doesn't affect next queries.

翻译中…

Input

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The first line of the input contains one integer $*q*$ ($1 ≤ *q* ≤ 500 000$) — the number of queries.

翻译中…

Then, $*q*$ lines follow. The $*i*$-th of them contains two integers $*type*_{*i*}$ and $*v*_{*i*}$ ($1 ≤ *type*_{*i*} ≤ 2$). If $*type*_{*i*} = 1$ then $*v*_{*i*}$ denotes a parent of a new vertex, while if $*type*_{*i*} = 2$ then you should print the answer for a subtree rooted in $*v*_{*i*}$.

翻译中…

It's guaranteed that there will be at least $1$ query of the second type, that is, the output won't be empty.

翻译中…

It's guaranteed that just before the $*i*$-th query a vertex $*v*_{*i*}$ already exists.

翻译中…

Output

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For each query of the second type print one real number —the expected value of the penalty if Limak attacks the given subtree. Your answer will be considered correct if its absolute or relative error does not exceed $10^{ - 6}$.

翻译中…

Namely: let's assume that your answer is $*a*$, and the answer of the jury is $*b*$. The checker program will consider your answer correct if image.

翻译中…

Note

翻译中…

Below, you can see the drawing for the first sample. Red circles denote queries of the second type.

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image

翻译中…

样例

Input #1
7
1 1
1 1
2 1
1 2
1 3
2 2
2 1
Output #1
0.7500000000
0.5000000000
1.1875000000
InputCopy OutputCopy
Input #2
8
2 1
1 1
1 2
1 3
1 4
2 1
1 4
2 1
Output #2
0.0000000000
0.9375000000
0.9687500000
InputCopy OutputCopy
题目信息
题号
643E
时间限制
5 s
内存限制
512 MB
标签
动态规划
数学
概率论
树

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。