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 (≤) 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 componentswhere 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<iostream>
#include<vector>
#include<set>
#include<algorithm>
using namespace std;
const int inf=10010;
vector<vector<int>> v;
set<int> s;
vector<int> temp;
int book[inf],maxh=0;
void dfs(int node,int height)
{
    if(height>maxh)
    {
        temp.clear() ;
        temp.push_back(node);
        maxh=height;
    }
    else if(height==maxh)
    {
        temp.push_back(node); 
    }
    book[node]=1;
    for(int i=0;i<v[node].size() ;i++)
    {
        if(book[v[node][i]]!=1)
        {
            dfs(v[node][i],height+1);
        }
    }
}
int main()
{
    int m,s1,a,b,cnt=0;
    cin>>m;
    v.resize(m + 1);
    for(int i=1;i<m;i++)
    {
        scanf("%d%d", &a, &b);
        v[a].push_back(b);
        v[b].push_back(a);
    }
    fill(book,book+inf,0);
    for(int i=1;i<=m;i++)
    {
        if(book[i]==0)
        {
            dfs(i,1);
            if(i==1)
            {
                if(temp.size()!=0) s1=temp[0];
                for(int j=0;j<temp.size();j++)
                s.insert(temp[j]);
            }
            cnt++;
        }
    }
    if(cnt>=2)
    printf("Error: %d components
",cnt);
    else{
        temp.clear();
        fill(book,book+inf,0);
        dfs(s1,1);
        for(int i=0;i<temp.size();i++)
            s.insert(temp[i]);
        for(auto it=s.begin() ;it!=s.end() ;it++)
        cout<<*it<<endl;
    }
    return 0;
} 

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