Submission #161602

#	Time	Username	Problem	Language	Result	Execution time	Memory
161602		amoo_safar	Mousetrap (CEOI17_mousetrap)	C++14	25 / 100	1054 ms	94284 KiB

mousetrap

#include <bits/stdc++.h>
 
#define pb push_back
#define F first
#define S second
 
using namespace std;
 
typedef long long ll;
typedef string str;
 
const ll Mod = 1e9 + 7;
const int Maxn = 1e6 + 100;

vector<ll> G[Maxn];
ll dp[Maxn], son[Maxn], m1[Maxn], m2[Maxn];
ll t, m;
vector<ll> V;
bool DFS(ll u, ll p){
	bool res = (u == m), r2;
	ll cnt = 0;
	ll mx = 0;
	ll mx2 = 0;
	
	for(auto adj : G[u]){
		if(adj == p) continue;
		r2 =DFS(adj, u);
		res |= r2;
		if(!r2){
			cnt ++;
			if(dp[adj] > mx){
				mx2 = mx;
				mx = dp[adj];
			} else mx2 = max(mx2, dp[adj]);
		}
	}
	dp[u] = cnt + mx2;
	m2[u] = mx2;
	m1[u] = mx;
	son[u] = cnt;
	if(res){
		V.pb(u);
	}
	return res;
}
ll dp2[Maxn];
int main(){
	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	ll n;
	cin >> n >> t >> m;
	ll u, v;
	for(int i = 1; i < n; i++){
		cin >> u >> v;
		G[u].pb(v);
		G[v].pb(u);
	}
	DFS(t, -1);
	
	
	ll sz = V.size();
	dp2[sz-1] = 0;
	ll sm = 0;
	for(int i = sz - 2; i >= 0; i--){
		dp2[i] = min( max(dp2[i + 1], sm + m1[V[i]] + son[V[i]]), 1LL + max(dp2[i + 1], sm + m2[V[i]] + son[V[i]] - 1) );
		sm += son[V[i]];
	}
	
	cout << dp2[0] << '\n';
	
	
	return 0;
}

• Subtask 1: 0 / 20
• Subtask 2: 25 / 25
• Subtask 3: 0 / 20
• Subtask 4: 0 / 35