跟poj1860类似 判断是否存在正环,bellman-ford每个点做一次正环判断,刚开始以为每种货币都要能升值,错了,后来又因为case后面少打了个空格 晕
code
#include <set> #include <map> #include <ctime> #include <queue> #include <cmath> #include <stack> #include <limits> #include <vector> #include <bitset> #include <string> #include <cstdio> #include <cstring> #include <fstream> #include <string.h> #include <iostream> #include <algorithm> #define Si set<int> #define LL long long #define pb push_back #define PS printf(" ") #define Vi vector<int> #define LN printf("\n") #define lson l,m,rt << 1 #define rson m+1,r,rt<<1|1 #define SD(a) scanf("%d",&a) #define PD(a) printf("%d",a) #define SET(a,b) memset(a,b,sizeof(a)) #define FF(i,a) for(int i(0);i<(a);i++) #define FD(i,a) for(int i(a);i>=(1);i--) #define FOR(i,a,b) for(int i(a);i<=(b);i++) #define FOD(i,a,b) for(int i(a);i>=(b);i--) #define readf freopen("input.txt","r",stdin) #define writef freopen("output.txt","w",stdout) const int maxn = 201; const long long BigP=999983; const int INF = 0x3fffffff; const int dx[]={0,1,0,-1}; const int dy[]={1,0,-1,0}; const double pi = acos(-1.0); const double eps= 1e-7; using namespace std; int N,M,e_cnt; char name[31][50]; double dis[maxn]; struct edge{ int from,to; double w; }E[501]; void add_E(int from,int to,double w){ E[++e_cnt].to=to; E[e_cnt].w=w; E[e_cnt].from=from; } bool bellman_ford(int s){ SET(dis,0); dis[s]=1; bool flag; while(dis[s]<=1+eps){ flag=false; FOR(i,0,e_cnt){ if(dis[E[i].to]<dis[E[i].from]*E[i].w){ dis[E[i].to]=dis[E[i].from]*E[i].w; flag=true; } } if(!flag){ if(dis[s]>1+eps) return true; else return false; } } return true; } int main(){ int cnt=1; while(~SD(N) &&N){ e_cnt=0; FOR(i,1,N){ scanf("%s",name[i]); } char ch[50];int k1,k2;double t; SD(M); FOR(i,1,M){ scanf("%s",ch); FOR(j,1,N){ if(!strcmp(ch,name[j])){ k1=j; } } scanf("%lf",&t); scanf("%s",ch); FOR(j,1,N){ if(!strcmp(ch,name[j])){ k2=j; } } add_E(k1,k2,t); } printf("Case %d: ",cnt++); bool flag=false; FOR(i,1,N){ if(bellman_ford(i)){ flag=true; break; } } if(flag) puts("Yes"); else puts("No"); } return 0; }