2240 

  1 /*
  2     判断是否存在正环
  3     居然还有同种货币的兑换，此点很。。。
  4 */
  5 
  6 // include file
  7 #include <cstdio>
  8 #include <cstdlib>
  9 #include <cstring>
 10 #include <cmath>
 11 #include <cctype>
 12 #include <ctime>
 13 
 14 #include <iostream>
 15 #include <sstream>
 16 #include <fstream>
 17 #include <iomanip>
 18 #include <bitset>
 19 #include <strstream>
 20 
 21 #include <algorithm>
 22 #include <string>
 23 #include <vector>
 24 #include <queue>
 25 #include <set>
 26 #include <list>
 27 #include <functional>
 28 
 29 using namespace std;
 30 
 31 // typedef
 32 typedef long long LL;
 33 typedef unsigned long long ULL;
 34 
 35 // 
 36 #define read freopen("in.txt","r",stdin)
 37 #define write freopen("out.txt","w",stdout)
 38 #define FORi(a,b,c) for(int i=(a);i<(b);i+=c)
 39 #define FORj(a,b,c) for(int j=(a);j<(b);j+=c)
 40 #define FORk(a,b,c) for(int k=(a);k<(b);k+=c)
 41 #define FORp(a,b,c) for(int p=(a);p<(b);p+=c)
 42 
 43 #define FF(i,a)    for(int i=0;i<(a);i+++)
 44 #define FFD(i,a)   for(int i=(a)-1;i>=0;i--)
 45 #define Z(a) (a<<1)
 46 #define Y(a) (a>>1)
 47 
 48 const double eps = 1e-6;
 49 const double INFf = 1e10;
 50 const int INFi = 1000000000;
 51 const double Pi = acos(-1.0);
 52 
 53 template<class T> inline T sqr(T a){return a*a;}
 54 template<class T> inline T TMAX(T x,T y)
 55 {
 56     if(x>y) return x;
 57     return y;
 58 }
 59 template<class T> inline T TMIN(T x,T y)
 60 {
 61     if(x<y) return x;
 62     return y;
 63 }
 64 template<class T> inline void SWAP(T &x,T &y)
 65 {
 66     T t = x;
 67     x = y;
 68     y = t;
 69 }
 70 template<class T> inline T MMAX(T x,T y,T z)
 71 {
 72     return TMAX(TMAX(x,y),z);
 73 }
 74 
 75 
 76 // code begin
 77 #define MAXN 35
 78 int N,M;
 79 bool F[MAXN][MAXN];
 80 double G[MAXN][MAXN];
 81 double dst[MAXN];
 82 char name[MAXN][30];
 83 
 84 int getdx(char *tar)
 85 {
 86     FORi(1,N+1,1)
 87     {
 88         if( strcmp(tar,name[i])==0 )
 89             return i;
 90     }
 91     return -1;
 92 }
 93 
 94 bool bellman_ford()
 95 {
 96 
 97         memset(dst,0,sizeof(dst));
 98         dst[1] = 1.0;
 99 
100         FORi(2,N+1,1)
101         {
102             FORj(1,N+1,1)
103             {
104                 FORk(1,N+1,1)
105                 {
106                     if( F[j][k] )
107                     {
108                         if( dst[j]*G[j][k]>dst[k] )
109                         {
110                             dst[k] = dst[j]*G[j][k];
111                         }
112                     }
113                 }
114             }
115         }
116 
117 
118         //
119         FORj(1,N+1,1)
120         {
121             FORk(1,N+1,1)
122             {
123                 if( F[j][k] )
124                 {
125                     if(dst[j]*G[j][k]>dst[k]) return true;
126                 }
127             }
128         }
129 
130     return false;
131 }
132 
133 int main()
134 {
135     read;
136     write;
137     char c1[30],c2[30];
138     double r;
139     int cas=1;
140     while(scanf("%d",&N)!=-1)
141     {
142         if(N==0) break;
143         FORi(1,N+1,1)
144         {
145             scanf("%s",name[i]);
146         }
147         memset(F,0,sizeof(bool)*MAXN*MAXN);
148         scanf("%d",&M);
149         while(M--)
150         {
151             scanf("%s %lf %s",c1,&r,c2);
152             int a = getdx(c1);
153             int b = getdx(c2);
154             F[a][b] = 1;
155             G[a][b] = r;
156         }
157         printf("Case %d: ",cas++);
158         if(bellman_ford()) printf("Yes\n");
159         else printf("No\n");
160     }
161     return 0;
162 }
posted @ 2011-03-03 14:53  AC2012  阅读(254)  评论(0)    收藏  举报