HAOI2006(BZOJ1050) 旅行comf

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#include<cstdio>

#include<cstdlib>

#include<algorithm>

const
int N = 510;

const
int M = 5010;

const
int Maxint = 2147483647;

using
namespace std;

#define For(i,n) for(int i=1;i<=n;i++)

#define Rep(i,l,r) for(int i=l;i<=r;i++)

struct
EDGE{

    int
s,t,next,w;

}E[M];

int
head[N],es=1,fa[N];

int
Max,Min = Maxint,n,m,x,y,w,s,t;

double
MIN = Maxint;

void
makelist(int
s,int t,int w){

    E[es].s = s;E[es].t = t;E[es].w = w;

    E[es].next = head[s];

    head[s]=es++;

}

void
init(){

    scanf("%d%d",&n,&m);

    For(i,m){

        scanf("%d%d%d",&x,&y,&w);

        makelist(x,y,w);

    }

    scanf("%d%d",&s,&t);

}

bool
cmp(EDGE A,EDGE B){

    return
A.w<B.w;

}

int
find(int
root){

    if(root!=fa[root]) fa[root] = find(fa[root]);

    return
fa[root];

}

int
gcd(int
a,int b){

    if(!b) return
a;

    else  
return gcd(b,a%b);

}

int
main(){

    init();

    sort(E+1,E+m+1,cmp);

    For(i,m){

        For(j,n) fa[j] = j;

        Rep(j,i,m){

            int
fx = find(E[j].s) , fy = find(E[j].t);

            if(fx!=fy) fa[fx] = fy;

            fx = find(s); fy = find(t);

            if(fx==fy)

                if((double)E[j].w/(double)E[i].w<MIN){

                    MIN = (double)E[j].w / (double)E[i].w;

                    Min = E[i].w;

                    Max = E[j].w;

                    break;

                }

        }

    }

    if(Min==Maxint)  puts("IMPOSSIBLE");

    else{

        int
gcds = gcd(Max,Min);

        if(Max%Min) printf("%d/%d\n",Max/gcds,Min/gcds);

        else       
printf("%d\n",Max/Min);

    }

    return
0;

}