Submission #1068178

#	Time	Username	Problem	Language	Result	Execution time	Memory
1068178		Muhammad_Aneeq	Highway Tolls (IOI18_highway)	C++17	18 / 100	109 ms	36960 KiB

highway

#include <vector>
#include <iostream>
#include <map>
#include "highway.h"
using namespace std;
int const MAXN=1e5;
vector<int>w;
long long dis=0;
vector<pair<int,int>>nei[MAXN]={};
int B1,A1;
vector<pair<int,int>>edges;
vector<int>ed[MAXN]={};
int h[MAXN]={};
int p[MAXN]={};
vector<int>d;
vector<int>g;
int it[MAXN],ot[MAXN];
int tm=0;
void dfs(int u,int pa=-1)
{
	it[u]=tm++;
	p[u]=pa;
	for (auto [i,in]:nei[u])
	{
		if (i==pa)
			continue;
		ed[h[u]].push_back(in);
		h[i]=h[u]+1;
		dfs(i,u);
	}
	ot[u]=tm-1;
}
bool check(int mid)
{
	for (int i=mid;i<MAXN;i++)
	{
		for (auto j:ed[i])
			w[j]=1;
	}
	long long g=ask(w);
	for (int i=mid;i<MAXN;i++)
	{
		for (auto j:ed[i])
			w[j]=0;
	}
	return (g!=dis);
}
bool check1(int mid,int z)
{
	for (int i=mid;i<MAXN;i++)
	{
		for (auto j:ed[i])
		{
			int x=edges[j].first;
			if (it[x]<=it[z]&&ot[x]>=ot[z])
				continue;
			w[j]=1;
		}
	}
	long long g=ask(w);
	for (int i=mid;i<MAXN;i++)
	{
		for (auto j:ed[i])
			w[j]=0;
	}
	return (g!=dis);	
}
void divi(int st,int en)
{
	if (st==en)
	{
		d.push_back(g[en]);
		return;
	}
	int mid=(st+en)/2;
	for (int i=st;i<=mid;i++)
		w[g[i]]=1;
	long long co=ask(w);
	for (int i=st;i<=mid;i++)
		w[g[i]]=0;
	if (co>dis)
		divi(st,mid);
	for (int i=mid+1;i<=en;i++)
		w[g[i]]=1;
	co=ask(w);
	for (int i=mid+1;i<=en;i++)
		w[g[i]]=0;
	if (co>dis)
		divi(mid+1,en);
}
void find_pair(int N, vector<int> U, vector<int> V, int A, int B)
{
	A1=A,B1=B;
	int m=U.size();
	for (int i=0;i<m;i++)
	{
		nei[U[i]].push_back({V[i],i});
		nei[V[i]].push_back({U[i],i});
	}
	dfs(0);
	for (int i=0;i<m;i++)
	{
		if (h[U[i]]>h[V[i]])
			swap(U[i],V[i]);
		edges.push_back({U[i],V[i]});
	}
	w.resize(m,0);
	dis=ask(w);
	h[0]=0;
	int st=0,en=N;
	while (st+1<en)
	{
		int mid=(st+en)/2;
		if (check(mid))
			st=mid;
		else
			en=mid;
	}
	for (auto i:ed[st])
		g.push_back(i);
	divi(0,g.size()-1);
	if (d.size()==2)
		answer(edges[d[0]].second,edges[d[1]].second);
	else
	{
		en=st;
		st=-1;
		int z=edges[d[0]].second;
		while (st+1<en)
		{
			int mid=(st+en)/2;
			if (check1(mid,z))
				st=mid;
			else
				en=mid;
		}
		if (st==-1)
		{
			int len=dis/A;
			int x=z;
			while (len--)
				x=p[x];
			answer(z,x);
			return;
		}
		d={};
		for (auto i:ed[st])
		{
			int x=edges[i].first;
			if (it[x]<=it[z]&&ot[x]>=ot[z])
				continue;
			g.push_back(i);
		}
		divi(0,g.size()-1);
		answer(z,edges[d[0]].second);
	}
}

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