oj.uz

Submission #374989

# Submission time Handle Problem Language Result Execution time Memory
374989 2021-03-08T18:39:37 Z YJU Mousetrap (CEOI17_mousetrap) C++14
25 / 100
 813 ms 79724 KB 
#include<bits/stdc++.h>
#pragma GCC optimize("unroll-loops,no-stack-protector,Ofast")
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pll;
const ll MOD=1e9+7;
const ll MOD2=998244353;
const ll N=1e6+5;
const ld pi=acos(-1);
const ll INF=(1LL<<30);
#define SQ(i) ((i)*(i))
#define REP(i,n) for(ll i=0;i<n;i++)
#define REP1(i,n) for(ll i=1;i<=n;i++)
#define pb push_back
#define mp make_pair
#define X first
#define Y second
#define setp setprecision
#define lwb lower_bound
#define SZ(_a) (ll)_a.size()

ll n,t,s,dp[N],x,y,fa[N],dg[N];
vector<ll> v[N],lis;

void DFS(ll nd,ll pa){
	
	fa[nd]=pa;
	
	ll ma=0,mb=0;
	for(auto i:v[nd]){
		if(i==pa)continue;
		DFS(i,nd);
		if(dp[i]>=ma)mb=ma,ma=dp[i];
		else if(dp[i]>=mb)mb=dp[i];
	}
	dp[nd]=mb+SZ(v[nd])-1;
}

bool ck(ll k){
	ll ti=0;
	REP(i,SZ(lis)-1){
		ll tmp=0;
		for(auto j:v[lis[i]]){
			if(j==lis[i+1]||(i&&j==lis[i-1]))continue;
			if(dg[i]+dp[j]+1+(i==0?0:-1)>k)++tmp;
		}
		ti+=tmp;k-=tmp;
		if(k<0||ti>i+1)return 0;
	}
	return 1;
}

int main(){
	ios_base::sync_with_stdio(0);cin.tie(0);
	cin>>n>>t>>s;
	REP(i,n-1)cin>>x>>y,v[x].pb(y),v[y].pb(x);
	
	if(s==t){cout<<"0\n";return 0;}
	
	DFS(t,0);
	dp[t]=0;
	x=s;
	while(x!=t)lis.pb(x),x=fa[x];
	lis.pb(t);
	
	for(int i=SZ(lis)-2;i>=0;i--)dg[i]=dg[i+1]+SZ(v[lis[i]])-1-(lis[i]==t?0:1);
	ll r=INF,l=0;
	while(l<r-1){
		ll mid=(r+l)>>1;
		(ck(mid)?r=mid:l=mid);
	}
	cout<<r<<"\n";
	return 0;
}

Subtask #1
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 16 ms 23788 KB Output is correct
2 Correct 17 ms 23808 KB Output is correct
3 Incorrect 16 ms 23788 KB Output isn't correct
4 Halted 0 ms 0 KB -

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 338 ms 79724 KB Output is correct
2 Correct 299 ms 74220 KB Output is correct
3 Correct 803 ms 78060 KB Output is correct
4 Correct 382 ms 51564 KB Output is correct
5 Correct 806 ms 78072 KB Output is correct
6 Correct 813 ms 78108 KB Output is correct

Subtask #3
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 16 ms 23788 KB Output is correct
2 Correct 17 ms 23808 KB Output is correct
3 Incorrect 16 ms 23788 KB Output isn't correct
4 Halted 0 ms 0 KB -

Subtask #4
0 / 35.0

# Verdict Execution time Memory Grader output
1 Correct 16 ms 23788 KB Output is correct
2 Correct 17 ms 23808 KB Output is correct
3 Incorrect 16 ms 23788 KB Output isn't correct
4 Halted 0 ms 0 KB -