1021. Deepest Root (25)

最新推荐文章于 2020-11-02 12:36:26 发布

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本文介绍了一种算法，用于在给定的连通无环图（即树）中找到能够生成最高树的根节点，并提供了相应的C++实现代码。若图不是一棵树，则输出错误信息并给出连通组件的数量。

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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<iostream>
#include<vector>
#include<algorithm>
#include<string.h>
using namespace std;
vector<int> node[10010];
bool visited[10010];
vector<int> out;
void init(){
    memset(visited,false,10010);
}
int maxdeep=0;
void dfs(int k,int deep,int &tmax){
    if(!visited[k]){
        if(tmax<deep) 
            tmax=deep;
        visited[k]=true;
        for(int i=0;i<node[k].size();i++){
           dfs(node[k][i],deep+1,tmax);
        }
    }
}
int main(){
    freopen("in.txt","r",stdin);
    int n,c1,c2,components=0;
    scanf("%d",&n);
    for(int i=1;i<n;i++){
        scanf("%d%d",&c1,&c2);
        node[c1].push_back(c2);
        node[c2].push_back(c1);
    }
    for(int i=1;i<=n;i++)
    {
        int t=0;
        if(!visited[i]){
            components++;
            dfs(i,1,t);
        }
    }
    if(components==1){
    for(int i=1;i<=n;i++){
        init();
        int tmax=0;
        dfs(i,1,tmax);
        if(tmax>maxdeep){
            maxdeep=tmax;
            out.clear();
            out.push_back(i);
        }
        else if(tmax==maxdeep){
            out.push_back(i);
        }
    }
    sort(out.begin(),out.end());
    for(int i=0;i<out.size();i++){
        printf("%d\n",out[i]);
    }
    }
    else printf("Error: %d components",components);
    return 0;
}