Codeforces Global Round 13
E
Fib-tree
Codeforces
2400
原题
← DF →
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Let $F_k$ denote the $k$-th term of Fibonacci sequence, defined as below:

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  • $F_0 = F_1 = 1$
  • for any integer $n \geq 0$, $F_{n+2} = F_{n+1} + F_n$
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You are given a tree with $n$ vertices. Recall that a tree is a connected undirected graph without cycles.

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We call a tree a Fib-tree, if its number of vertices equals $F_k$ for some $k$, and at least one of the following conditions holds:

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  • The tree consists of only $1$ vertex;
  • You can divide it into two Fib-trees by removing some edge of the tree.
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Determine whether the given tree is a Fib-tree or not.

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Input

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The first line of the input contains a single integer $n$ ($1 \leq n \leq 2 \cdot 10^5$) — the number of vertices in the tree.

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Then $n-1$ lines follow, each of which contains two integers $u$ and $v$ ($1\leq u,v \leq n$, $u \neq v$), representing an edge between vertices $u$ and $v$. It's guaranteed that given edges form a tree.

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Output

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Print "YES" if the given tree is a Fib-tree, or "NO" otherwise.

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You can print your answer in any case. For example, if the answer is "YES", then the output "Yes" or "yeS" will also be considered as correct answer.

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Note

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In the first sample, we can cut the edge $(1, 2)$, and the tree will be split into $2$ trees of sizes $1$ and $2$ correspondently. Any tree of size $2$ is a Fib-tree, as it can be split into $2$ trees of size $1$.

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In the second sample, no matter what edge we cut, the tree will be split into $2$ trees of sizes $1$ and $4$. As $4$ isn't $F_k$ for any $k$, it's not Fib-tree.

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In the third sample, here is one possible order of cutting the edges so that all the trees in the process are Fib-trees: $(1, 3), (1, 2), (4, 5), (3, 4)$.

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样例

Input #1
3
1 2
2 3
Output #1
YES
InputCopy OutputCopy
Input #2
5
1 2
1 3
1 4
1 5
Output #2
NO
InputCopy OutputCopy
Input #3
5
1 3
1 2
4 5
3 4
Output #3
YES
InputCopy OutputCopy
题目信息
题号
1491E
时间限制
1 s
内存限制
256 MB
标签
暴力
DFS 及类似
分治
数论
树

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