1021. Deepest Root (25)

时间限制

1500 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

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 (<=10000) 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:

5
1 2
1 3
1 4
2 5

Sample Output 1:

3
4
5

Sample Input 2:

5
1 3
1 4
2 5
3 4

Sample Output 2:

Error: 2 components

#include<fstream>
#include <cstdio>
#include <iostream>
#include<algorithm>
#include<set>
#include<map>
#include<vector>
#include<string>
#include<cmath>
using namespace std;
int n, maxheight = 0;
vector<vector<int>> v;
bool visit[10010];
set<int> s;
vector<int> temp;
void dfs(int node, int height) {
if(height > maxheight) {
temp.clear();
temp.push_back(node);
maxheight = height;
} else if(height == maxheight){
temp.push_back(node);
}
visit[node] = true;
for(int i = 0; i < v[node].size(); i++) {
if(visit[v[node][i]] == false)
dfs(v[node][i], height + 1);
}
}
int main()
{
#ifdef _DEBUG
ifstream cin("a.txt");
#endif
scanf("%d", &n);
v.resize(n + 1);
int a, b, cnt = 0, s1 = 0;
for(int i = 0; i < n - 1; i++) {
scanf("%d%d", &a, &b);
v[a].push_back(b);
v[b].push_back(a);
}
for(int i = 1; i <= n; i++) {
if(visit[i] == false) {
dfs(i, 1);
if(i == 1) {
for(int j = 0; j < temp.size(); j++) {
s.insert(temp[j]);
if(j == 0) s1 = temp[j];
}
}
cnt++;
}
}
if(cnt >= 2) {
printf("Error: %d components", cnt);
} else {
temp.clear();
maxheight = 0;
fill(visit, visit + 10010, false);
dfs(s1, 1);
for(int i = 0; i < temp.size(); i++)
s.insert(temp[i]);
for(auto it = s.begin(); it != s.end(); it++)
printf("%d\n", *it);
}

#ifdef _DEBUG
cin.close();
system("pause");
#endif

return 0;

}