Submission #1309179

#	Time	Username	Problem	Language	Result	Execution time	Memory
1309179		JuanJL	Race (IOI11_race)	C++20	21 / 100	3095 ms	14352 KiB

race

#include "race.h"
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>

#define fst first
#define snd second
#define pb push_back
#define forn(i,a,b) for(int i = a; i<b; i++)
#define SZ(x) (int)x.size()
#define ALL(x) x.begin(),x.end()
#define mset(a,v) memset(a,v,sizeof(a))
#define FIN ios::sync_with_stdio(0); cout.tie(); cin.tie(0);
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
template <typename L>
using iset = tree<L,null_type,less<L>,rb_tree_tag,tree_order_statistics_node_update>;

const int MAXN = 200000+5;

ll n;
ll k;
vector<pair<ll,ll>> adj[MAXN];
bool cen[MAXN];
ll subsz[MAXN];

void calcsz(ll nd, ll p){
	subsz[nd]=1;
	for(auto i:adj[nd])if(i.fst!=p && !cen[i.fst])calcsz(i.fst,nd);
	for(auto i:adj[nd])if(i.fst!=p && !cen[i.fst])subsz[nd]+=subsz[i.fst];
}

void calcpath(ll nd, ll p, ll sz, ll dep, unordered_map<ll,ll> &path){
	
	if(path[sz]!=0) path[sz]=min(path[sz],dep);
	else path[sz]=dep;

	for(auto i:adj[nd])if(i.fst!=p && !cen[i.fst]){
		calcpath(i.fst,nd,sz+i.snd,dep+1,path);
	}
}

ll find_centroid(ll nd, ll p){
	for(auto i:adj[nd])if(i.fst!=p && !cen[i.fst]){
		if(subsz[i.fst]*2>=n){
			return find_centroid(i.fst,nd);
		}
	}
	cen[nd]=true;
	return nd;
}

ll rres = 1000000000;

void solve(){
	queue<ll> cola; cola.push(0);
	while(!cola.empty()){
		ll nd=cola.front();
		cola.pop();

		calcsz(nd,-1);
		ll c = -1;
		if(subsz[nd]>1) c=find_centroid(nd,-1);
		if(c==-1) continue;

		//cout<<"Nuevo centroide "<<c<<'\n';

		ll res = 1000000000;
		unordered_map<ll,ll> paths;
		for(auto i:adj[c]) if(!cen[i.fst]){
			unordered_map<ll,ll> pathc;
			calcpath(i.fst,c,i.snd,1,pathc);

			for(auto [szchild,rdep]:pathc) if(paths[k-szchild]){
				res=min(res,rdep+paths[k-szchild]);
			}

			for(auto [szchild,rdep]:pathc) if(!paths[szchild]){
				paths[szchild]=rdep;
				if(szchild==k) res=min(res,rdep);
			}else{
				paths[szchild]=min(paths[szchild],rdep);
			}

			cola.push(i.fst);
			
		}

		rres=min(rres,res);
	}
}


int best_path(int N, int K, int H[][2], int L[])
{
	//cout<<"inica\n";
	FIN;
	n = N;
	k = K;
	forn(i,0,n-1){
		adj[H[i][0]].pb({H[i][1],L[i]});
		adj[H[i][1]].pb({H[i][0],L[i]});
	}

	//cout<<"llamando a solve\n";

	solve();

//	cout<<rres<<'\n';

  	return (rres!=1000000000?rres:-1);
}

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