PTA甲级——1021

1021 Deepest Root

A graph which is connected and acyclic can be considered a tree. The height of the tree depends on the selected root. Now you are supposed to find the root that results in a highest tree. Such a root is called the deepest root.

Input Specification:

Each input file contains one test case. For each case, the first line contains a positive integer N (≤104) which is the number of nodes, and hence the nodes are numbered from 1 to N. Then N−1 lines follow, each describes an edge by given the two adjacent nodes’ numbers.

Output Specification:

For each test case, print each of the deepest roots in a line. If such a root is not unique, print them in increasing order of their numbers. In case that the given graph is not a tree, print Error: K components where K is the number of connected components in the graph.

Sample Input 1:

1
2
3
4
5
5
1 2
1 3
1 4
2 5

Sample Output 1:

1
2
3
3
4
5

Sample Input 2:

1
2
3
4
5
5
1 3
1 4
2 5
3 4

Sample Output 2:

1
Error: 2 components

思路

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代码

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