HNACM(六)--第三题 最舒适的路线

用并查集,枚举下界,可以参考HDU1598题。

#include<stdio.h>#include<stdlib.h>#include<string.h>#include<math.h>#include<ctype.h>#define INF 30000#define MAXN 500+10#define N 5000+10int f[MAXN];struct PATH{int x;int y;int v;}d[N];int cmp(const void *a,const void *b){return (*(PATH *)a).v - (*(PATH *)b).v;}int common(int m,int n){int t,i;if(m < n){ t = m; m = n; n = t;}for(i = n; i > 0; i--) if(m%i == 0&&n%i == 0)return i;}int getfather(int x){if(x != f[x])f[x] = getfather(f[x]);return f[x];}int Union(int x,int y){int fx = getfather(x);int fy = getfather(y);if(fx != fy)f[fx] = fy;return 0;}int main(){//freopen("test.txt","r",stdin);int max,min,cmn,from,to,x,y,v,k,n,m,i,j;double rate;scanf("%d",&k);while(k--){max = -INF;min = INF;rate = INF*1.0;scanf("%d%d",&n,&m);//for(i = 1; i <= n; i++)//f[i] = i;for(i = 0; i < m; i++)scanf("%d%d%d",&d[i].x,&d[i].y,&d[i].v);qsort(d,m,sizeof(PATH),cmp);scanf("%d%d",&from,&to);for(i = 0; i < m; i++){for(j = 1; j <= n; j++)f[j] = j;for(j = i; j < m; j++){Union(d[j].x,d[j].y);if(getfather(from) == getfather(to))break;}if(j < m){double r = (d[j].v*1.0)/(d[i].v*1.0);if(r < rate){rate = r;max = d[j].v;min = d[i].v;}}}if(rate == INF*1.0)printf("IMPOSSIBLE\n");else{if(max%min == 0)printf("%d\n",max/min);else{cmn = common(max,min);printf("%d/%d\n",max/cmn,min/cmn);}}}return 0;}