EVENCYCLE
Problem
Given an undirected graph consisting of vertices and edges, find a cycle with an even number of edges, if it exists.
Input:
The first line of the input will contain a positive integer , the number of queries to answer. Each of the next queries will begin with a line containing two natural numbers and separated by a space: the number of vertices and the number of edges of the graph. Following this, there will be lines, each containing two natural numbers and separated by a space, representing an edge between vertices and . Assume vertices are numbered from to , and no two edges connecting the same pair of vertices in the graph will be given.
Output:
The output should contain exactly lines, each one corresponding to an answer to a query in the order they are given. Each answer line will contain either:
- The word "cycle", followed by an even positive integer (the number of edges in the cycle), followed by integers , , , . This answer indicates that the requested cycle has been found. To be valid, such an answer must satisfy (as a single edge is not considered a cycle), the numbers , , , must be pairwise distinct vertices of the cycle, there must be an edge (,\; ) for each , and there must also be an edge to complete the cycle. If there are multiple cycles with an even number of edges, you may print any of them.
- The word "none", if there is no cycle with an even number of edges. All words and numbers on each line of the output should be separated in pairs by a single space.
Constraints
- and . Of course, it will be true that .
- and for every edge given, and also .
- The sum of all queries will not exceed , and the sum of all queries will not exceed .
- Time Limit: sec.
Memory Limit: MB.
For test cases with a total value of , it will be .
- For test cases with a total value of , it will be and .
- For test cases with a total value of , the vertices of the graph can be colored using two colors in such a way that there are no edges between vertices of the same color.
- For test cases with a total value of , each vertex of the graph will be connected to at most two other vertices.
- For test cases with a total value of , each vertex of the graph will be connected to at most three other vertices (and there will be vertices that are connected exactly to three other vertices.).
- For the rest of the test cases with a total value of , none of the above special constraints will apply..
Example of Input - Output Files:
Note: For your convenience, in the example that follows, the three input queries are separated from each other.
evencycle.in | evencycle.out | |
4 5 1 2 1 3 2 3 3 4 4 1 |
cycle 4 3 2 1 4 | |
5 6 1 2 1 3 1 4 1 5 2 3 4 5 |
none | |
7 6 1 7 3 4 4 5 5 6 6 3 5 2 |
cycle 4 6 3 4 5 |
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