hdu 1217——Arbitrage

弗洛伊德演算法，就是下面三重迴圈。

for(i=0;i<n;i++)for(j=0;j<n;j++)for(k=0;k<n;k++)if(map[j][i]*map[i][k]>map[j][k])map[j][k]=map[j][i]*map[i][k];

代碼

#include<cstdio>#include<cstring>#include<iostream>using namespace std;char str[33][33],ch1[33],ch2[33];double n,map[33][33],dis[33];int Num(char ch[],int n){int i;for(i=0;i<n;i++)if(strcmp(str[i],ch)==0)return i;}int main(){double cost;int n,m,s,e,flag;int i,j,k,num=1;;while(scanf("%d%*c",&n)!=EOF&&n){memset(map,0,sizeof(map));for(i=0;i<n;i++)scanf("%s%*c",str[i]);scanf("%d%*c",&m);for(i=0;i<m;i++){ cin>>ch1>>cost>>ch2;s=Num(ch1,n);e=Num(ch2,n);map[s][e]=cost;}flag=0;for(i=0;i<n;i++)for(j=0;j<n;j++)for(k=0;k<n;k++)if(map[j][i]*map[i][k]>map[j][k]){map[j][k]=map[j][i]*map[i][k];if(map[0][0]>1){flag=1;break;}}if(flag)printf("Case %d: Yes\n",num);elseprintf("Case %d: No\n",num);num++;getchar();}return 0;}