Cod sursa(job #1755171)

Utilizator howsiweiHow Si Wei howsiwei Data 9 septembrie 2016 15:23:24
Problema Algoritmul Bellman-Ford Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.64 kb
#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <list>
using namespace std;

const int oo = 0x3f3f3f3f;
const int S = 0;

int main() {
	ios::sync_with_stdio(false);
	freopen("bellmanford.in", "r", stdin);
	freopen("bellmanford.out", "w", stdout);
	int n, m;
	cin >> n >> m;
	vector<vector<pair<int,int>>> adjl(n);
	for (int i = 0; i < m; i++) {
		int u, v, w;
		cin >> u >> v >> w;
		u--, v--;
		adjl[u].emplace_back(w, v);
	}
	vector<int> dist(n, oo);
	dist[S] = 0;
	list<int> q;
	q.push_back(S);
	vector<list<int>::iterator> posQ(n, q.end());
	posQ[S] = q.begin();
	list<pair<int,int>> t {{0, S}, {0, 0}};
	vector<list<pair<int,int>>::iterator> posT(n, t.end());
	posT[S] = t.begin();
	// int nrelax = 0;
	do {
		auto u = q.front();
		q.pop_front();
		posQ[u] = q.end();
		for (auto e: adjl[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 (posT[v] != t.end()) {
					int lvl = posT[v]->first;
					auto it = t.erase(posT[v]);
					while (it->first > lvl) {
						int x = it->second;
						if (x == u) {
							puts("Ciclu negativ!");
							return 0;
						}
						if (posQ[x] != q.end()) {
							q.erase(posQ[x]);
							posQ[x] = q.end();
						}
						dist[x] += dif+1;
						posT[x] = t.end();
						it = t.erase(it);
					}
				}
				posT[v] = t.emplace(next(posT[u]), posT[u]->first+1, v);
				if (posQ[v] == q.end()) {
					q.push_back(v);
					posQ[v] = prev(q.end());
				}
				// nrelax++;
			}
		}
	} while (!q.empty());
	// printf("%d\n", nrelax);
	for (int i = 1; i < n; i++) {
		printf("%d%c", dist[i],  " \n"[i == n-1]);
	}
}