图论最短路之spfa

#include
#include
#include
#include
using namespace std ;
const int INF = 1000000 ;
const int maxn = 10 ;
struct ArcNode
{
	int to ;
	int weight ;
	ArcNode *next ;
};
queue Q ;
int n ;
ArcNode *List[ maxn ] ;
int inq[ maxn ]  ;
int dist[ maxn ] , path[ maxn ] ;
void SPFA( int src )
{
	int i , u ;
	ArcNode * temp ;
	for( i = 0 ; i < n ; i++ )
	{
		dist[ i ] = INF ;
		path[ i ] = src ;
		inq[ i ] = 0 ;
	}
	dist[ src ] = 0 ;
	path[ src ] = src ;
	inq[ src ]++ ;
	Q.push( src ) ;
	while( !Q.empty() )
	{
		u = Q.front() ;
		Q.pop() ;
		inq[ u ]-- ;
		temp = List[ u ] ;
		while( temp != NULL )
		{
			int v= temp-> to ;
			if( dist[ v ] > dist[ u ] + temp->weight )
			{
				dist[ v ] = dist[ u ] + temp -> weight ;
				path[ v ] = u ;
				if( !inq[ v ] )
				{
					Q.push( v ) ;
					inq[ v ]++ ;
				}
			}
			temp = temp -> next ;
		}
	}
}

int main()
{
	int  i , j ;
	int u , v , w ;
	scanf( "%d" , &n );
	memset( List , 0 , sizeof( List ) ) ;
	ArcNode *temp ;
	while( 1 ) 
	{
		scanf( "%d%d%d" ,&u , &v , &w ) ;
		if( u == -1 && v == -1 && w == -1 )
			break ;
		temp = new ArcNode ;
		temp -> to = v ;
		temp -> weight = w;
		temp -> next = NULL ;
		if( List[ u ] == NULL )
			List[ u ] = temp ;
		else
		{
			temp -> next = List[ u ] ;
			List[ u ] = temp ;
		}
	}
	SPFA( 0 ) ;
	for( j = 0 ; j < n ; j++ )
	{
		temp = List[ j ] ;
		while( temp != NULL )
		{
			List[ j ] = temp -> next ;
			delete temp ;
			temp = List[ j ] ;
		}
	}
	int shortest[ maxn ] ;
	for( i = 1 ; i < n ; i++ )
	{
		printf( "%d\t" , dist[ i ] ) ;
		memset( shortest , 0 , sizeof( shortest ) ) ;
		int k = 0 ;
		shortest[ k ] = i ;
		while( path[ shortest[ k ] ] != 0 )
		{
			k++ ;
			shortest[ k ] = path[ shortest[ k - 1 ] ] ;
		}
		k++ ;
		shortest[ k ] = 0 ;
		for( j = k ; j > 0 ; j-- )
			printf( "%d->" , shortest[ j ] ) ;
		printf( "%d\n" , shortest[ 0 ] ) ;
	}
}

/*

7
0 1 6
0 2 5
0 3 5
1 4 -1
2 1 -2
2 4 1
3 2 -2
3 5 -1
4 6 3
5 6 3
-1 -1 -1
1       0->3->2->1
3       0->3->2
5       0->3
0       0->3->2->1->4
4       0->3->5
3       0->3->2->1->4->6

*/