Mai intai trebuie sa te autentifici.
Cod sursa(job #1463837)
Utilizator | Data | 21 iulie 2015 16:22:11 | |
---|---|---|---|
Problema | Algoritmul Bellman-Ford | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 2.11 kb |
#include <fstream>
#include <vector>
#include <queue>
#include <cstring>
#include <algorithm>
#define NMAX 50001
#define INF 10002
#define pb push_back
#define mp make_pair
#define nod first
#define cost second
using namespace std;
ifstream fin ( "bellmanford.in" ) ;
ofstream fout ( "bellmanford.out" ) ;
vector< pair < int, int > > Graph [NMAX] ;
vector< pair < int, int > > ::iterator vec ;
queue< int > Q ;
int N, M, i, x, y, c, D[NMAX], It, iterari_nod [NMAX], Nod;
bool in_queue [NMAX];
int main()
{
fin >> N >> M;
for( ; M--; )
{
fin >> x >> y >> c;
Graph [x].pb( mp( y, c ) );
}
memset( in_queue , false , sizeof(in_queue) ) ; //initial nu avem noduri in coada
memset( D , INF , sizeof(D) ) ; //toate distantele sunt infinit
D[1] = 0 ; //mai putin cea pana la sursa
memset( iterari_nod , 0 , sizeof(iterari_nod) ) ; //nu s-a trecut niciodata prin niciun nod
Q.push( 1 ) ; //introducem nodul 1 in coada
in_queue [1] = true;
while( !Q.empty() )
{
Nod = Q.front();
Q.pop();
in_queue [Nod] = false; // scoatem nodul din coada
for( vec = Graph [Nod].begin(); vec != Graph [Nod].end(); vec ++ ) // iteram prin vecinii nodului
if( D [ (*vec).nod ] > D[Nod] + (*vec).cost ) // incercand sa minimizam distanta pana la acestia
{
D [ (*vec).nod ] = D[Nod] + (*vec).cost ;
if( !in_queue [(*vec).nod] ) // daca nodul nu se afla in coada
{
Q.push( (*vec).nod ) ; // il introducem
in_queue [(*vec).nod] = true ;
if( ++ iterari_nod [ (*vec).nod ] > N ) // daca s-a trecut de mai mult de N ori prin el
{
fout << "Ciclu negativ!\n"; // inseamna ca in graf exista un ciclu negativ
return 0;
}
}
}
}
for( i = 2; i <= N; ++ i )
fout << D[i] << ' '; // distantele de la nodul 1( sursa ) pana la celelalte noduri
return 0;
}