Submission #5540311

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Source Code Expand

#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<complex>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
using namespace std;
typedef long long ll;
typedef unsigned long long ul;
typedef unsigned int ui;
const ll mod = 1000000007;
typedef double ld;
typedef complex<ld> Point;
const ll INF = mod * mod;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
const ld eps = 1e-6;
const ld pi = acos(-1.0);
typedef pair<ld, ld> LDP;
typedef pair<ll, ll> LP;

void solve() {
	int n; cin >> n;
	vector<vector<int>> G(n);
	rep(i, n - 1) {
		int a, b; cin >> a >> b; a--; b--;
		G[a].push_back(b);
		G[b].push_back(a);
	}
	queue<int> q;
	vector<bool> used(n);
	int r = n;
	rep(i, n) {
		if (G[i].size() == 1) {
			q.push(i);
			used[i] = true;
			r--;
		}
	}
	int tmp = 0;
	while (true) {
		if (r == 0) {
			vector<bool> exi(n,false);
			while (!q.empty()) {
				int id = q.front(); q.pop();
				exi[id] = true;
			}
			bool g = false;
			rep(j, n)if (exi[j]) {
				rep(i, G[j].size()) {
					int to = G[j][i]; if (exi[to]) {
						g=true; break;
					}
				}
			}
			if (g)tmp++;
			break;
		}
		tmp++;
		int len = q.size();
		rep (aa,len) {
			int id = q.front(); q.pop();
			rep(j, G[id].size()) {
				int to = G[id][j];
				if (used[to])continue;
				used[to] = true; r--; q.push(to);
			}
		}
	}
	int s = 1; int k = 1;
	while (true) {
		if (tmp <= s)break;
		s = s * 2 + 1; k++;
	}
	//cout << tmp << endl;
	cout << k << endl;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	//cout << fixed << setprecision(9);
	solve();
	//stop
	return 0;
}

Submission Info

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