hdu1217 Arbitrage

3
USDollar
BritishPound
FrenchFranc
3
USDollar 0.5 BritishPound
BritishPound 10.0 FrenchFranc
FrenchFranc 0.21 USDollar

3
USDollar
BritishPound
FrenchFranc
6
USDollar 0.5 BritishPound
USDollar 4.9 FrenchFranc
BritishPound 10.0 FrenchFranc
BritishPound 1.99 USDollar
FrenchFranc 0.09 BritishPound
FrenchFranc 0.19 USDollar

0

Case 1: Yes
Case 2: No
这题可以用floyd和map做，map用来存货币的种类，再用floyd判断经过其他货币中转到自己的时候有没有汇率大于1的情况。


#include<stdio.h>
#include<map>
#include<string.h>
#include<string>
#include<algorithm>
using namespace std;
char s[100][100],s1[100],s2[100];
double dis[100][100];
int flag,n,index;
double max(double a,double b)
{
	return a>b?a:b;
}


void floyd()
{
	int i,j,k;
	for(k=1;k<=index;k++){
		for(i=1;i<=index;i++){
			for(j=1;j<=index;j++){
				dis[i][j]=max(dis[i][j],dis[i][k]*dis[k][j]);
			}
		}
	}
	for(i=1;i<=index;i++){
		if(dis[i][i]>1){
			flag=1;break;
		}
	}
	return;
}


int main()
{
	int m,i,j,num=0;
	double a;
	while(scanf("%d",&n)!=EOF && n!=0)
	{
		map<string,int> hash;
		hash.clear();
		memset(dis,0,sizeof(dis));
		index=0;
		for(i=1;i<=n;i++){
			scanf("%s",s[i]);
			if(hash[s[i]]==0){
				index++;
				hash[s[i]]=index;
			}
		}
		flag=0;
		scanf("%d",&m);
		for(i=1;i<=m;i++){
			scanf("%s%lf%s",s1,&a,s2);
			if(strcmp(s1,s2)==0 && a>1)
			flag=1;
			if(dis[hash[s1]][hash[s2]]<a){
				dis[hash[s1]][hash[s2]]=a;
			}
		}
		printf("Case %d: ",++num);
		//printf("%d\n\n",index);
		if(flag==1){
			printf("Yes\n");continue;
		}
		
		floyd();
		if(flag)printf("Yes\n");
		else printf("No\n");
	}
	return 0;
}