1.pat 1021 deepest root 第4个测试点无法通过
2.代码：跟参考答案代码基本一致，只是变量名变了而已；求大神指出代码中无法通过测试的原因！谢谢

#include<cstdio>
#include<vector>
#include<algorithm>
using namespace std;

const int maxn=100010;

vector<int> adj[maxn];
bool root[maxn];
int father[maxn];

void init(int n)
{
    for(int i=1;i<=n;++i)
    {
        father[i]=i;
    }
}

int findfather(int x)
{
    int a=x;
    while(x!=father[x])
    {
        x=father[x];
    }
    
    while(a!=father[a])
    {
        int temp=a;
        a=father[a];
        father[temp]=x;
    }
    return x;
}
void sunion(int a, int b)
{
    int fa=father[a];
    int fb=father[b];
    if(fa!=fb) father[fb]=fa;
}

int blockcount(int n)
{
    int block=0;
    for(int i=1;i<=n;++i)
    {
        //int rt=findfather(i);
        root[findfather(i)]=true;
    }
    for(int i=1;i<=n;++i)
    {
        block+=root[i];
    }
    
    return block;
}


int maxheight=0;

vector<int> tempdeepest, ans;
void dfs(int vt, int height, int pre)
{
    if(height>maxheight)
    {
        tempdeepest.clear();
        tempdeepest.push_back(vt);
        maxheight=height;
    }
    else if(height==maxheight)
        tempdeepest.push_back(vt);
    

    for(int i=0;i<adj[vt].size();++i)
    {
        //int v=adj[vt][i];
        if(adj[vt][i]==pre) continue;
        dfs(adj[vt][i], height+1, vt);
    }
}

int main()
{
    int n;
    scanf("%d",&n);
    
    init(n);//忘记了；
    
    int va, vb;
    for(int i=1;i<n;++i)//n-1条边；
    {
        //int va, vb;
        scanf("%d%d", &va, &vb);
        adj[va].push_back(vb);
        adj[vb].push_back(va);
        sunion(va, vb);
    }
    
    int block=blockcount(n);
    
    if(block!=1)
        printf("Error: %d components\n", block);
    else
    {
        dfs(1, 1,-1);
        
        ans=tempdeepest;
        dfs(ans[0],1,-1);
        for(int i=0;i<tempdeepest.size();++i)
        {
            //int rt=tempdeepest[i];
            ans.push_back(tempdeepest[i]);
        }
        
        sort(ans.begin(), ans.end());
        printf("%d\n",ans[0]);
        for(int i=1;i<ans.size();++i)
        {
            if(ans[i]!=ans[i-1])
                printf("%d\n", ans[i]);
        }
    }
    return 0;
}