cses tree solution.cpp

// please accept this as hacktoberfest-accepted label
//problem link
//  https://cses.fi/problemset/task/2079
//hope you like it
//thanks


#include<bits/stdc++.h>
using namespace std;
 
 
 
#define ll long long
#define ld long double
#define rep(i,a,b) for(ll i=a;i<b;i++)
#define repb(i,a,b) for(ll i=a;i>=b;i--)
#define err() cout<<"--------------------------"<<endl; 
#define errA(A) for(auto i:A)   cout<<i<<" ";cout<<endl;
#define err1(a) cout<<#a<<" "<<a<<endl
 
 
 
#define err2(a,b) cout<<#a<<" "<<a<<" "<<#b<<" "<<b<<endl
#define err3(a,b,c) cout<<#a<<" "<<a<<" "<<#b<<" "<<b<<" "<<#c<<" "<<c<<endl
#define err4(a,b,c,d) cout<<#a<<" "<<a<<" "<<#b<<" "<<b<<" "<<#c<<" "<<c<<" "<<#d<<" "<<d<<endl
#define pb push_back
#define all(A)  A.begin(),A.end()
#define allr(A)    A.rbegin(),A.rend()
#define ft first
#define sd second
 
#define pii pair<int,int>
#define pll pair<ll,ll>
#define V vector<ll>
#define S set<ll>
#define VV vector<V>
#define Vpll vector<pll>
 
#define endl "\n"


ll binaryexp(ll a,ll b,ll i)
{
    if(b==0)
        return 1LL;
    if(b==1)
        return a;
    ll k=binaryexp(a,b/2,i);
    if(b&1)
    {
        return (((k*k)%i)*a)%i;
    }
    else
        return (k*k)%i;
}
V sz(200005,0);
void dfs(VV &a,int i,int p)
{
    for(auto x:a[i])
    {
        if(x!=p)
        {
            dfs(a,x,i);
            sz[i]+=sz[x];
        }
 
    }
    sz[i]+=1;
}
int nn;
int func(VV &a,int i,int p)
{
    for(auto x:a[i])
    {
        if(x!=p)
        {
            if(sz[x]>=nn)
            {
                return func(a,x,i);
            }
        }
    }
    return i;
}
int main()
    {
        ios_base::sync_with_stdio(false);
        cin.tie(NULL); cout.tie(NULL);
        #ifndef ONLINE_JUDGE
         clock_t tStart = clock();
        freopen("input.txt","r",stdin);
        freopen("output.txt","w",stdout);
        #endif
        int t;
        // cin>>t;
        t=1;
           
        while(t--)
        {
            int n;
            cin>>n;
            VV a(n);
            rep(i,0,n-1)
            {
                int x,y;
                cin>>x>>y;
                x-=1;
                y-=1;
                a[x].pb(y);
                a[y].pb(x);
            }
            nn=(n+1)/2;
            dfs(a,0,-1);
            // rep(i,0,n)
            // {
            //     cout<<sz[i]<<" ";
            // }
            // err1(nn);
            cout<<func(a,0,-1)+1;
 
 
        }
        #ifndef ONLINE_JUDGE
            printf("\nRun Time -> %.10fs\n", (double)(clock()-tStart) / CLOCKS_PER_SEC);
            #endif
}