Codeforces Round 360 (Div. 2)
C
NP-Hard Problem
Codeforces
未评级
原题
← BD →
翻译中…

Recently, Pari and Arya did some research about NP-Hard problems and they found the minimum vertex cover problem very interesting.

翻译中…

Suppose the graph $*G*$ is given. Subset $*A*$ of its vertices is called a vertex cover of this graph, if for each edge $*uv*$ there is at least one endpoint of it in this set, i.e. image or image (or both).

翻译中…

Pari and Arya have won a great undirected graph as an award in a team contest. Now they have to split it in two parts, but both of them want their parts of the graph to be a vertex cover.

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They have agreed to give you their graph and you need to find two disjoint subsets of its vertices $*A*$ and $*B*$, such that both $*A*$ and $*B*$ are vertex cover or claim it's impossible. Each vertex should be given to no more than one of the friends (or you can even keep it for yourself).

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Input

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The first line of the input contains two integers $*n*$ and $*m*$ ($2 ≤ *n* ≤ 100 000$, $1 ≤ *m* ≤ 100 000$) — the number of vertices and the number of edges in the prize graph, respectively.

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Each of the next $*m*$ lines contains a pair of integers $*u*_{*i*}$ and $*v*_{*i*}$ ($1  ≤  *u*_{*i*},  *v*_{*i*}  ≤  *n*$), denoting an undirected edge between $*u*_{*i*}$ and $*v*_{*i*}$. It's guaranteed the graph won't contain any self-loops or multiple edges.

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Output

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If it's impossible to split the graph between Pari and Arya as they expect, print "-1" (without quotes).

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If there are two disjoint sets of vertices, such that both sets are vertex cover, print their descriptions. Each description must contain two lines. The first line contains a single integer $*k*$ denoting the number of vertices in that vertex cover, and the second line contains $*k*$ integers — the indices of vertices. Note that because of $*m* ≥ 1$, vertex cover cannot be empty.

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Note

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In the first sample, you can give the vertex number $2$ to Arya and vertices numbered $1$ and $3$ to Pari and keep vertex number $4$ for yourself (or give it someone, if you wish).

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In the second sample, there is no way to satisfy both Pari and Arya.

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样例

Input #1
4 2
1 2
2 3
Output #1
1
2
2
1 3
InputCopy OutputCopy
Input #2
3 3
1 2
2 3
1 3
Output #2
-1
InputCopy OutputCopy
题目信息
题号
688C
时间限制
2 s
内存限制
256 MB

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