Cod sursa(job #544637)

Utilizator BitOneSAlexandru BitOne Data 1 martie 2011 21:03:53
Problema Algoritmul lui Dijkstra Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.69 kb
#include <vector>
#include <fstream>
#include <cstdlib>
#define N_MAX 50011
#define oo 1<<20
#define pr pair< int, int >

using namespace std;
int lHeap;
int H[N_MAX], P[N_MAX], d[N_MAX];
vector< pr > G[N_MAX];
vector< pr >::const_iterator it, iend;
inline void _swap( int& x, int& y ) { int aux=x; x=y; y=aux; }
inline int _min( int x, int y ) { return ( x <= y ? x : y ); }
inline int _max( int x, int y ) { return ( x >= y ? x : y ); }
void DownHeap( int k )
{
	for( int son=2*k; son <= lHeap; son=2*k )
	{
		if( son < lHeap && d[H[son+1]] < d[H[son]] )
			++son;
		if( d[H[k]] <= d[H[son]] )
			return;
		_swap( H[k], H[son] );
		P[H[k]]=k;
		P[H[son]]=son;
		k=son;
	}
}
void UpHeap( int k )
{
	for( int key=d[H[k]], f=k/2; k > 1 && key < d[H[f]]; k=f, f/=2 )
	{
		_swap( H[k], H[f] );
		P[H[k]]=k;
		P[H[f]]=f;
	}
}
inline int pop()
{
	int r=H[1];
	H[1]=H[lHeap];
	P[H[1]]=1;
	--lHeap;
	DownHeap( 1 );
	return r;
}
inline void push( int k, int dist )
{
	d[k]=dist;
	H[++lHeap]=k;
	P[k]=lHeap;
	UpHeap( lHeap );
}
int main( void )
{
	int N, M, x, y, c;
	ifstream in( "dijkstra.in" );
	for( in>>N>>M; M; --M )
	{
		in>>x>>y>>c;
		G[x].push_back( pr(y, c) );
	}
	for( x=1; x <= N; ++x )
		d[x]=oo;
	for( push( 1, 0 ); lHeap; )
	{
		x=pop();
		for( it=G[x].begin(), iend=G[x].end(); it < iend; ++it )
			if( d[it->first] > d[x]+it->second )
			{
				if( oo == d[it->first] )
					push( it->first, d[x]+it->second );
				else {
						d[it->first]=d[x]+it->second;
						UpHeap( P[it->first] );
					 }
			}
	}
	ofstream out( "dijkstra.out" );
	for( x=2; x <= N; ++x )
		out<<( oo == d[x] ? 0 : d[x] )<<' ';
	out<<'\n';
	return EXIT_SUCCESS;
}