Submission #136486

#	Time	Username	Problem	Language	Result	Execution time	Memory
136486		amiratou	Highway Tolls (IOI18_highway)	C++14	18 / 100	202 ms	13508 KiB

highway

#include "highway.h"
#include <bits/stdc++.h>
#define ll long long
#define ii pair<int,int>
#define fi first
#define se second
#define pb push_back
using namespace std;
vector<vector<ii> > vec;
vector<int> query;
vector<ii> target;
ll dist,a,b;
void dfs(int node,int high,int p){
	if(high!=-1)target.pb(ii(high,node));
	for(auto child:vec[node])
		if(child.fi!=p)
			dfs(child.fi,child.se,node);
}
void dfs2(int node,ll d,int high,int p){
	if(d*a==dist){
		target.pb(ii(high,node));
		return;
	}
	for(auto child:vec[node])
		if(child.fi!=p)
			dfs2(child.fi,d+1,child.se,node);
}
void find_pair(int N, vector<int> U, vector<int> V, int A, int B) {
	int M = U.size();
	a=A,b=B;
	vec.resize(N);
	query.resize(M);
	bool subtask=1;
	for (int i = 0; i < M; ++i)
	{
		vec[U[i]].pb(ii(V[i],i));
		vec[V[i]].pb(ii(U[i],i));
		if(U[i]!=i||V[i]!=i+1)subtask=0;
	}
	if(subtask){
		int start=0;
		for (int i = 0; i < N; ++i)
		{
			if(vec[i].size()==1){
				start=i;
				break;
			}
		}
		fill(query.begin(),query.end(),0);
		dist=ask(query);
		dfs(start,-1,0);
		//sort(target.begin(),target.end());
		int l=0,r=(int)(target.size())-1;
		int n1=-1,n2=-1,L=0;
		while(l<r){
			int med=(l+r)>>1;
			L=med;
			fill(query.begin(),query.end(),0);
			for (int i = l; i <= med; ++i)
				query[target[i].fi]=1;
			ll check=ask(query);
			if(check==dist)
				l=med+1;
			else if(check==(dist/A)*B){
				r=med;
			}
			else{
				ll nb_edges=(check-dist)/(B-A);
				//cerr<<l<<" "<<r<<" "<<nb_edges<<" "<<med<<"\n";
				n1=(((med-nb_edges)<0)?start:target[med-nb_edges].se);
				n2=target[med+(dist-nb_edges*A)/A].se;
				//cerr<<n1<<" "<<n2<<"\n";
				break;
			}
		}
		if(n1!=-1)
			answer(n1, n2);
		else
			answer((L?target[L-1].se:start),target[L].se);
	}
	else{
		fill(query.begin(),query.end(),0);
		dist=ask(query);
		dfs2(0,0,-1,0);
		sort(target.begin(),target.end());
		int l=0,r=(int)target.size()-1,ans=0;
		while(l<=r){
			int med=(l+r)>>1;
			fill(query.begin(),query.end(),0);
			for (int i = l; i <= med; ++i)
				query[target[i].fi]=1;
			ll check=ask(query);
			if(check!=dist){
				ans=med;
				r=med-1;
			}
			else l=med+1;
		}
		answer(0, target[ans].se);
	}
}

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 6 / 6
• Subtask 4: 0 / 33
• Subtask 5: 0 / 18
• Subtask 6: 0 / 31