Submission #240509

#	Time	Username	Problem	Language	Result	Execution time	Memory
240509		c4ts0up	Dreaming (IOI13_dreaming)	C++14	14 / 100	106 ms	13744 KiB

dreaming

#include "dreaming.h"
#include <bits/stdc++.h>
#define ll long long
#define pb push_back
#define ff first
#define ss second
using namespace std;

const ll INF = 1e15;
const ll NMAX = 1e5+5;

struct Vertex {
	int id, parent;
	ll pdist;

	Vertex () {}
	Vertex (int x) { id = x; }
};

struct Graph {
	vector <Vertex> V;
	vector <pair <ll, int> > Adj[NMAX];
	vector <bool> vis;
	int excluded = -1, sze;

	Graph () {}
	Graph (int s) {
        sze = s;
		V.resize(sze);
		for (int i=0; i<s; i++) V[i] = Vertex(i);
	}

	// Hace una DFS y devuelve el nodo más lejano
	pair <ll,int> DFS(int o) {
	    //cerr << "Entrando a DFS..." << endl;
		vector <ll> dist;
		stack <pair <int,int> > to;

		dist.resize(sze);
		vis.resize(sze);
		for (int i=0; i<sze; i++) dist[i] = INF, vis[i] = false;

		// Hace la DFS
		to.push({0LL, o});
		dist[o] = 0;
		while (!to.empty()) {
			pair <int, ll> curr = to.top();
			//cerr << "Visitando " << curr.ss << " (distancia acc " << curr.ff << ")" << endl;
			to.pop();
			dist[curr.ss] = curr.ff;
			vis[curr.ss] = true;

			for (pair <ll, int> p : Adj[curr.ss]) {
				if (!vis[p.ss]) to.push({p.ff + curr.ff, p.ss}), V[p.ss].parent = curr.ss, V[p.ss].pdist = p.ff;
			}
		}

		// Encuentra el más lejano
		pair <ll, int> best = {-1, -1};
		for (int i=0; i<sze; i++) {
			// No pertence a esta componente
			if (!vis[i]) {
				excluded = i;
				continue;
			}

			if (dist[i] != 0) best = max(best, {dist[i], i});
		}

		return best;
	}

	ll Diametro() {
		// Devuelve el diametro
		pair <ll, int> rx = DFS(0);
		pair <ll, int> ry = DFS(rx.ss);
		return ry.ff;
	}

	// Encuentra el radio. Devuele el centro
	int Radio(int o = 0) {
	    //cerr << "--- PRIMERA DFS ---" << endl;
		pair <ll, int> rx = DFS(o);
		//cerr << "(" << rx.ff << ", " << rx.ss << ")" << endl;
		//cerr << "El excluido es " << excluded << endl;
        //cerr << "--- SEGUNDA DFS ---" << endl;
		pair <ll, int> ry = DFS(rx.ss);
		//cerr << "(" << ry.ff << ", " << ry.ss << ")" << endl;

		int curr = ry.ss;
		int best = curr;
		ll a = ry.ff, b = 0;
		ll maxi = INF;

        //cerr << "--- BUSCANDO RADIO ---" << endl;
		while (curr != rx.ss) {
            //cerr << "Revisando " << curr << endl;
			if (max(a,b) < maxi) best = curr, maxi = max(a,b);

			a -= V[curr].pdist;
			b += V[curr].pdist;

			curr = V[curr].parent;
		}

		return best;
	}
};

Graph G;

int travelTime(int n, int m, int l, int A[], int B[], int T[]) {
	G = Graph(n);
	//cerr << "Creando grafo... OK" << endl;

	for (int i=0; i<m; i++) {
		G.Adj[A[i]].pb({T[i], B[i]});
		G.Adj[B[i]].pb({T[i], A[i]});
	}

	//cerr << "Llenando grafo... OK" << endl;

	int g1 = G.Radio();
	//cerr << "Primer centro " << g1 << endl;
	int g2 = G.Radio(G.excluded);
	//cerr << "Segundo centro " << g2 << endl;
	G.Adj[g2].pb({(ll)(l), g1});
	G.Adj[g1].pb({(ll)(l), g2});

	return G.Diametro();
}

• Subtask 1: 14 / 14
• Subtask 2: 0 / 10
• Subtask 3: 0 / 23
• Subtask 4: 0 / 18
• Subtask 5: 0 / 12
• Subtask 6: 0 / 23