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  • 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 N1 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;
    } 

    多多学习stl吧

    如果你够坚强够勇敢,你就能驾驭他们
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  • 原文地址:https://www.cnblogs.com/liuzhaojun/p/11264895.html
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