Submission #1575174

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
typedef pair<int,P> P1;
typedef pair<P,P> P2;
#define pu push
#define pb push_back
#define mp make_pair
#define eps 1e-7
#define INF 1000000000
#define mod 1000000007
#define fi first
#define sc second
#define rep(i,x) for(int i=0;i<x;i++)
#define repn(i,x) for(int i=1;i<=x;i++)
#define SORT(x) sort(x.begin(),x.end())
#define ERASE(x) x.erase(unique(x.begin(),x.end()),x.end())
#define POSL(x,v) (lower_bound(x.begin(),x.end(),v)-x.begin())
#define POSU(x,v) (upper_bound(x.begin(),x.end(),v)-x.begin())
//very good problem
vector<int>edge[100005];
int n;
int dfs(int v,int u){
	int cnt[20]={}; vector<int>vec;
	for(int i=0;i<edge[v].size();i++){
		if(u == edge[v][i]) continue;
		int y = dfs(edge[v][i],v);
		rep(j,20) if(((y>>j)&1)) cnt[j]++;
		vec.pb(y);
	}
	int mx = INF;
	for(int j=19;j>=0;j--){
		if(cnt[j] == 0) mx=j;
		else if(cnt[j] >= 2) break;
	}
	int ret = (1<<mx);
	for(int i=0;i<vec.size();i++){
		int x = vec[i]/(1<<mx) * (1<<mx);
		ret |= x;
	}
	return ret;
}
int main(){
	cin>>n;
	rep(i,n-1){
		int a,b;cin>>a>>b;
		edge[a].pb(b);
		edge[b].pb(a);
	}
	int x = dfs(1,-1);
	rep(i,20) if(((x>>(19-i))&1)) {cout<<19-i<<endl;return 0;}
}

Submission Info

Judge Result