zoj2750Idiomatic Phrases Game

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=1750

#include<stdio.h>
#include<string.h>
#define MAXN 1000
#define INF 1000000000

struct idiom
{
	char front[ 5 ] ,back [ 5 ] ;
	int T ;
};
idiom dic[ MAXN ];
int Edge[ MAXN ][ MAXN] ;
int dist[ MAXN ] ;
int S[ MAXN ] ;
int N ;


int main()
{
	int  i , j , k ;
	char s[ 100 ] ;
	int len ;
	while( scanf( "%d" ,&N ) != EOF )
	{
		if( N == 0 )
			break;
		for( k = 0 ; k < N ; k++ )
		{
			scanf( "%d%s" , &dic[ k ].T  , s  ) ;
			len = strlen ( s ) ;
			for( i = 0 , j = len - 1; i < 4 ; i++ , j-- )
			{
				dic[ k ].front[ i ] = s[ i ] ;
				dic[ k ].back[ 3 - i ] = s[ j ] ;
			}
			dic[ k ].back[4] = dic[ k ].front[ 4 ] = '\0' ;
		}
		for( i = 0 ; i < N ; i++ )
		{
			for( j = 0 ; j < N ; j++ )
			{
				Edge[ i ][ j ] = INF ;
				if( i == j )
					continue ;
				if( strcmp( dic[ i ].back , dic[ j ].front ) == 0 )
					Edge[ i ][ j ] = dic[ i ].T ;
			}
		}
		
		for( i = 0 ; i < N ; i++ )
		{
			dist[ i ] = Edge[ 0 ][ i ] ;
			S[ i ] =  0 ;
		}
		S[ 0 ] = 1 ;
		dist[ 0 ] =  0 ;
		for( i = 0 ; i < N - 1; i++ )
		{
			int min = INF ;
			int u = 0 ;
			for( j = 0 ; j < N ; j++ )
			{
				if( !S[ j ] && dist[ j ] < min )
				{
					u = j ;
					min = dist[ j ] ;
				}
			}
			S[ u ] = 1 ;
			for( k = 0 ; k < N ; k++ )
			{
				if( !S[ k ] && Edge[ u ][ k ] < INF && Edge[ u ][ k ] + dist[ u ] < dist[ k ] )
					dist[ k ] = dist[ u ] + Edge[ u ][ k ] ;
			}
		}
		if( dist[ N - 1] == INF )
			printf( "-1\n" ) ;
		else
			printf( "%d\n" , dist[ N -1 ] );
	}
	return 0 ;
}