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Cod sursa(job #435588)
# include <fstream>
# include <vector>
using namespace std;
//Bellman Ford algorithm with a queue ( using BFS )
//supposed to obtain 100p.
struct neighbour{
int y, c;
};
int dist [ 50001 ], queue[50001], qs;
bool viz[50001];
vector <neighbour> G [ 50001 ];
const int inf = 2000000001;
int main(){
ifstream f ( "bellmanford.in" );
ofstream g ( "bellmanford.out" );
int n, m, i, x, h;
bool ok = 1;
neighbour a;
vector <neighbour> :: iterator it, end;
f >> n >> m;
for ( i = 0; i < m; ++ i ){
f >> x >> a . y >> a . c ;
G [ x ] . push_back ( a );
}
f . close ();
for ( i = 2; i <= n; ++ i )
dist [ i ] = inf;
for ( i = 1; i < n && ok; ++ i ){
h=0; qs = 0;
queue [ qs ++ ] = 1;
memset ( viz, 0, sizeof ( viz ) );
ok = 0;
while ( h < qs ){
end = G [ queue [ h ] ] . end ();
for ( it = G [ queue [ h ] ] . begin (); it != end; ++ it ){
if ( ! viz [ it -> y ] )
queue [ qs ++ ] = it -> y;
viz [ it -> y ] = 1;
if ( dist [ it -> y ] > dist [ queue [ h ] ] + ( it -> c ) ){
dist [ it -> y ] = dist [ queue [ h ] ] + ( it -> c );
ok = 1;
}
}
++ h;
}
}
h=0; qs = 0;
queue [ qs ++ ] = 1;
memset ( viz, 0, sizeof ( viz ) );
while ( h < qs ){
end = G [ queue [ h ] ] . end ();
for ( it = G [ queue [ h ] ] . begin (); it != end; ++ it ){
if ( ! viz [ it -> y ] )
queue [ qs ++ ] = it -> y;
viz [ it -> y ] = 1;
if ( dist [ it -> y ] > dist [ queue [ h ] ] + ( it -> c ) ){
g << "Ciclu negativ!\n";
g . close ();
return 0;
}
}
++ h;
}
for ( i = 2; i <= n; ++ i )
g << dist [ i ] << ' ';
g << '\n';
g . close ();
return 0;
}