Cod sursa(job #1755250)

Utilizator howsiweiHow Si Wei howsiwei Data 9 septembrie 2016 17:21:45
Problema Algoritmul Bellman-Ford Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.63 kb
#include <iostream>
#include <cstdio>
#include <vector>
#include <queue>
#include <list>
using namespace std;

const int _ = 0;
const int oo = 0x3f3f3f3f;
const int s = 0;

int main() {
#ifdef INFOARENA
	freopen("bellmanford.in", "r", stdin);
	freopen("bellmanford.out", "w", stdout);
#endif
	cin.sync_with_stdio(false);
	int n, m;
	cin >> n >> m;
	vector<vector<pair<int,int>>> al(n);
	for (int i = 0; i < m; i++) {
		int u, v, w;
		cin >> u >> v >> w;
		u--, v--;
		al[u].emplace_back(w, v);
	}
	vector<int> dist(n, oo);
	dist[s] = 0;
	queue<int> q;
	q.push(s);
	vector<bool> inQ(n, false);
	inQ[s] = true;
	vector<bool> rlx(n, false);
	rlx[s] = true;
	list<pair<int,int>> t {{0, s}, {0, _}};
	vector<list<pair<int,int>>::iterator> pos(n, t.end());
	pos[s] = t.begin();
	// int nrelax = 0;
	while (!q.empty()) {
		auto u = q.front();
		q.pop();
		inQ[u] = false;
		if (!rlx[u]) continue;
		rlx[u] = false;
		for (auto e: al[u]) {
			int w = e.first;
			int v = e.second;
			if (dist[v] > dist[u]+w) {
				int dif = dist[u]+w-dist[v];
				dist[v] = dist[u]+w;
				if (pos[v] != t.end()) {
					int lvl = pos[v]->first;
					auto it = t.erase(pos[v]);
					while (it->first > lvl) {
						int x = it->second;
						if (x == u) {
							puts("Ciclu negativ!");
							return 0;
						}
						rlx[x] = false;
						dist[x] += dif+1;
						pos[x] = t.end();
						it = t.erase(it);
					}
				}
				pos[v] = t.emplace(next(pos[u]), pos[u]->first+1, v);
				rlx[v] = true;
				if (!inQ[v]) {
					q.push(v);
					inQ[v] = true;
				}
			}
			// nrelax++;
		}
	}
	for (int i = 1; i < n; i++) {
		printf("%d%c", dist[i],  " \n"[i == n-1]);
	}
	// printf("%d\n", nrelax);
}