HDU1599 最小环

floyd新应用！！！！

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 1 #include<stdio.h>

 2 const int maxn = 101;

 3 const int inf = 9999999;

 4 int n,m;

 5 int dis[ maxn ][ maxn ],mat[ maxn ][ maxn ];

 6 

 7 void floyd(){

 8     int ans=inf;

 9     for( int i=1;i<=n;i++ )

10         for( int j=1;j<=n;j++ )

11             dis[ i ][ j ]=mat[ i ][ j ];

12     for( int k=1;k<=n;k++ ){

13 

14         for( int i=1;i<k;i++ ){

15             for( int j=1;j<i;j++ ){

16                 if( ans>( dis[i][j]+mat[i][k]+mat[k][j] ) )

17                     ans=dis[i][j]+mat[i][k]+mat[k][j];

18             }

19         }

20 

21         for( int i=1;i<=n;i++ ){

22             for( int j=1;j<=n;j++ ){

23                 if( dis[i][k]!=inf && dis[k][j]!=inf && dis[i][j]>(dis[i][k]+dis[k][j]) )

24                     dis[i][j]=(dis[i][k]+dis[k][j]);

25             }

26         }

27 

28     }

29 

30      if(ans==inf)

31          printf("It's impossible.\n");

32      else 

33          printf("%d\n",ans); 

34 }

35 

36 int main(){

37     while( scanf("%d%d",&n,&m)==2 ){

38         for( int i=1;i<=n;i++ )

39             for( int j=1;j<=n;j++ )

40                 mat[ i ][j ]=inf;

41         int a,b,c;

42         while( m-- ){

43             scanf("%d%d%d",&a,&b,&c);

44             if( c<mat[ a ][ b ] )

45                 mat[ a ][ b ]=mat[ b ][ a ]=c;

46         }

47         floyd();

48     }

49     return 0;

50 }