Submission #412554

#	Time	Username	Problem	Language	Result	Execution time	Memory
412554		jeqcho	Race (IOI11_race)	C++17	0 / 100	7 ms	11212 KiB

race

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<pair<int,int>> vpi;

#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a: x)

#define pb push_back
#define rsz resize
#define sz(x) int(x.size())
#define all(x) begin(x), end(x)
#define fi first
#define se second


// subtask 1,2,3

int const n=2e5;
unordered_map<int,int> adj[n];
int sub[n];
int const INF=1e9;
int mn=INF;
int k;

int getsub(int now, int par)
{
	sub[now]=1;
	trav(chi,adj[now])
	{
		if(chi.fi==par)continue;
		sub[now]+=getsub(chi.fi,now);
	}
	return sub[now];
}

int centroid(int now, int par, int siz)
{
	trav(chi,adj[now])
	{
		if(chi.fi==par)continue;
		if(sub[chi.fi]>siz/2)return centroid(chi.fi,now,siz);
	}
	return now;
}

int const k_=1e6+3;
pair<pii,pii> path[k_];
vi pos;
bitset<k_> got;

void dfs(int now, int par, int cur, int id, int dep)
{
	if(cur>k)return;
	if(!got[cur])
	{
		pos.pb(cur);
		got[cur]=1;
		path[cur] = {{INF,-1},{INF,-1}};
	}
	if(path[cur].fi.fi==id)
	{
		path[cur].fi.se = min(path[cur].fi.se,dep);
	}
	else if(path[cur].se.fi==id)
	{
		path[cur].se.se = min(path[cur].se.se,dep);
		if(path[cur].se.se < path[cur].fi.se)
		{
			swap(path[cur].se.se, path[cur].fi.se);
		}
	}
	else if(dep < path[cur].fi.se)
	{
		path[cur].se = path[cur].fi;
		path[cur].fi = {id,dep};
	}
	else if(dep < path[cur].se.se)
	{
		path[cur].se = {id,dep};
	}
	trav(chi,adj[now])
	{
		if(chi.fi==par)continue;
		dfs(chi.fi,now,cur+chi.se,id,dep+1);
	}
}

void solve(int now)
{
	pos.clear();
	trav(chi,adj[now])
	{
		dfs(chi.fi,now,chi.se,chi.fi,1);
	}
	pos.pb(0);
	path[0].fi={0,now};
	got[0]=1;
	trav(i,pos)
	{
		if(i>k/2)break;
		if(!got[k-i])continue;
		if(path[i].fi.fi==path[k-i].fi.fi)
		{
			if(path[i].se.fi!=-1)
			{
				mn=min(mn,path[i].se.se+path[k-i].fi.se);
			}
			if(path[i].fi.fi!=-1)
			{
				mn=min(mn,path[i].fi.se+path[k-i].se.se);
			}
		}
		else
		{
			mn=min(mn,path[i].fi.se+path[k-i].fi.se);
		}
	}
	trav(e,pos)
	{
		got[e]=0;
	}
}


void decomp(int now)
{
	int siz = getsub(now,-1);
	int u = centroid(now,-1,siz);
	solve(u);
	trav(chi,adj[u])
	{
		adj[chi.fi].erase(u);
		decomp(chi.fi);
	}
}

int best_path(int N, int K, int H[][2], int L[]){
	k=K;
	F0R(i,N-1)
	{
		int u = H[i][0];
		int v = H[i][1];
		adj[u].insert({v,L[i]});
		adj[v].insert({u,L[i]});
	}
	decomp(0);
	
	if(mn==INF)return -1;
	return mn;
}

• Subtask 1: 0 / 9
• Subtask 2: 0 / 12
• Subtask 3: 0 / 22
• Subtask 4: 0 / 57