Submission #1309165

#	Time	Username	Problem	Language	Result	Execution time	Memory
1309165		JuanJL	Race (IOI11_race)	C++20	21 / 100	3096 ms	59008 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 vis[MAXN];
bool cen[MAXN];
ll subsz[MAXN];
ll par[MAXN];
unordered_map<ll,ll> path[MAXN];

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

	for(auto i:adj[nd])if(i.fst!=p && !cen[i.fst]){
		for(auto [szchild,rdep]:path[i.fst]) if(!path[nd][szchild]){
			path[nd][szchild]=rdep;
		}
	}
}

ll find_centroid(ll nd){
	mset(subsz,-1);
	calcsz(nd,-1);
	/*cout<<"calcsz listo\n";
	forn(i,0,n) cout<<subsz[i]<<" "; cout<<'\n';*/
	if(subsz[nd]==1) return -1;
	forn(i,0,n)if(subsz[i]!=-1){
		bool is = true;
		for(auto j:adj[i]) if(j.fst!=par[i]){
			if(subsz[j.fst]*2>subsz[nd]){
				is=false;
			}
		}
		if(par[i]!=-1 && (subsz[nd]-subsz[i])*2>subsz[nd]) is=false;

		if(is){
			cen[i]=true;
			return i;
		}
	}
}

ll rres = 1000000000;

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

		ll c = find_centroid(nd);
		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]){
			calcpath(i.fst,c,i.snd,1);

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

			for(auto [szchild,rdep]:path[i.fst]) 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);
}

Compilation message (stderr)

race.cpp: In function 'll find_centroid(ll)':
race.cpp:71:1: warning: control reaches end of non-void function [-Wreturn-type]
   71 | }
      | ^

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