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| #include <bits/stdc++.h>
#define N 100005
#define ios ios::sync_with_stdio(0),cin.tie(0)
using namespace std;
int n,start,dis[N];
bool visit[N];
vector<int>edge[N];
int dfs(int id,int cur_dis){
if(visit[id])return 0;
visit[id] = 1;
int len = edge[id].size(),max_len=0;
for(int i=0;i<len;i++){
int next = edge[id][i];
if(visit[next])continue;
dis[next] = cur_dis+1;
int temp = dfs(next,cur_dis+1);
max_len = max(max_len,temp);
}
return max_len+1;
}
int main(){
ios;
cin>>n;
for(int i=0;i<n-1;i++){
int a,b;cin>>a>>b;
edge[a].push_back(b);
edge[b].push_back(a);
}
start = 0;
memset(visit,0,sizeof(visit));
int distance = dfs(2,0);distance--;
for(int i=0;i<n;i++){
if(dis[i]==distance){
start = i;
break;
}
}
memset(visit,0,sizeof(visit));
cout<<dfs(start,0)-1<<endl;
}
|