UVA 10099 The Tourist Guide
二分+并查集
二分枚举边权，再用并查集判连通
1 #include <iostream> 2 #include <cstdio> 3 #include <algorithm> 4 #include <cstring> 5 6 using namespace std; 7 const int MAXN=110; 8 const int MAXM=10100; 9 const int inf=50000000; 10 struct e{ 11 int u,v,w; 12 }edge[MAXM]; 13 int n,m; 14 int s,t,num; 15 16 bool cmp(struct e A,struct e B){ 17 if(A.w>B.w)return true; 18 return false; 19 } 20 int pre[MAXN],rank[MAXN]; 21 22 int find(int x){ 23 int r=x; 24 while(pre[r]!=-1) 25 r=pre[r]; 26 while(x!=r){ 27 int q=pre[x]; 28 pre[x]=r; 29 x=q; 30 } 31 return r; 32 } 33 34 bool slove(int mid){ 35 for(int i=0;i<m;i++){ 36 if(edge[i].w<mid) break; 37 int t1=find(edge[i].u); 38 int t2=find(edge[i].v); 39 if(t1==t2) continue; 40 if(rank[t1]>rank[t2]){ 41 pre[t2]=t1; 42 } 43 else if(rank[t2]<rank[t1]) 44 pre[t1]=t2; 45 else { 46 rank[t2]++; 47 pre[t1]=t2; 48 } 49 } 50 if(find(s)==find(t)) 51 return true; 52 return false; 53 } 54 55 int main(){ 56 int cas=0; 57 int u,v,w; 58 while(scanf("%d%d",&n,&m)!=EOF){ 59 if(n==0&&m==0) break; 60 cas++; 61 for(int i=0;i<m;i++){ 62 scanf("%d%d%d",&u,&v,&w); 63 edge[i].u=u;edge[i].v=v; 64 edge[i].w=w; 65 } 66 scanf("%d%d%d",&s,&t,&num); 67 sort(edge,edge+m,cmp); 68 int high=inf,low=0; 69 int ans=inf; 70 while(low<=high){ 71 int mid=(low+high)/2; 72 memset(pre,-1,sizeof(pre)); 73 memset(rank,0,sizeof(rank)); 74 if(slove(mid)){ 75 ans=mid; low=mid+1; 76 } 77 else high=mid-1; 78 } 79 int a=num/(ans-1)+(num%(ans-1)>0?1:0); 80 printf("Scenario #%d\n",cas); 81 printf("Minimum Number of Trips = %d\n\n",a); 82 } 83 return 0; 84 }
