题意：与poj1680一样，有不同的换钱渠道，可以完成特定两种货币的交换，并且有汇率，只不过此题是单向边，然后问是否能使财富增加
与poj1680一样，建图之后直接spfa判增值的环即可
1 #include<iostream>
2 #include<cstdio>
3 #include<string>
4 #include<cstring>
5 #include<queue>
6 #include<map>
7 #include<vector>
8 using namespace std;
9
10 int head[35],nxt[1000],point[1000],size;
11 double val[1000],dist[35];
12 bool vis[35];
13 int n,p,t[35];
14
15 void add(int a,int b,double v){
16 int i;
17 for(i=head[a];~i;i=nxt[i]){
18 if(point[i]==b){
19 if(val[i]<v)val[i]=v;
20 return;
21 }
22 }
23 point[size]=b;
24 val[size]=v;
25 nxt[size]=head[a];
26 head[a]=size++;
27 }
28
29 void spfa(){
30 int i;
31 memset(dist,0,sizeof(dist));
32 memset(vis,0,sizeof(vis));
33 memset(t,0,sizeof(t));
34 dist[1]=100;
35 vis[1]=1;
36 queue<int>q;
37 q.push(1);
38 bool f=1;
39 while(!q.empty()&&f){
40 int u=q.front();
41 q.pop();
42 vis[u]=0;
43 for(i=head[u];~i;i=nxt[i]){
44 int j=point[i];
45 double v=dist[u]*val[i];
46 if(dist[j]<v){
47 dist[j]=v;
48 if(!vis[j]){
49 q.push(j);
50 vis[j]=1;
51 t[j]++;
52 if(t[j]>n)f=0;
53 }
54 }
55 }
56 }
57 if(f)printf("Case %d: No
",++p);
58 else printf("Case %d: Yes
",++p);
59 }
60
61 int main(){
62 p=0;
63 while(scanf("%d",&n)!=EOF&&n!=0){
64 map<string,int>M;
65 int i;
66 string tmp;
67 memset(head,-1,sizeof(head));
68 size=0;
69 for(i=1;i<=n;i++){
70 cin>>tmp;
71 M[tmp]=i;
72 }
73 int m;
74 scanf("%d",&m);
75 for(i=1;i<=m;i++){
76 string t1,t2;
77 double a;
78 cin>>t1>>a>>t2;
79 add(M[t1],M[t2],a);
80 }
81 spfa();
82 }
83 return 0;
84 }