HDOJ 题目1217 Arbitrage(最短路径,Floyd)
2014-10-23 00:30
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ArbitrageTime Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 4737 Accepted Submission(s): 2162 Problem Description Arbitrage is the use of discrepancies in currency exchange rates to transform one unit of a currency into more than one unit of the same currency. For example, suppose that 1 US Dollar buys 0.5 British pound, 1 British pound buys 10.0 French francs, and 1 French franc buys 0.21 US dollar. Then, by converting currencies, a clever trader can start with 1 US dollar and buy 0.5 * 10.0 * 0.21 = 1.05 US dollars, making a profit of 5 percent. Your job is to write a program that takes a list of currency exchange rates as input and then determines whether arbitrage is possible or not. Input The input file will contain one or more test cases. Om the first line of each test case there is an integer n (1<=n<=30), representing the number of different currencies. The next n lines each contain the name of one currency. Within a name no spaces will appear. The next line contains one integer m, representing the length of the table to follow. The last m lines each contain the name ci of a source currency, a real number rij which represents the exchange rate from ci to cj and a name cj of the destination currency. Exchanges which do not appear in the table are impossible. Test cases are separated from each other by a blank line. Input is terminated by a value of zero (0) for n. Output For each test case, print one line telling whether arbitrage is possible or not in the format "Case case: Yes" respectively "Case case: No". Sample Input 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 Sample Output Case 1: Yes Case 2: No Source University of Ulm Local Contest 1996 Recommend Eddy | We have carefully selected several similar problems for you: 1142 1385 1301 1596 2112 Dijkstra算法不能处理带有负权值的最短路,但此题中,两种货币之间的兑换比率可能小于1 ac代码 #include<stdio.h> #include<string.h> #include<string> #include<map> #include<iostream> using namespace std; int n,m; double ma[50][50],rate; void init() { int i,j; for(i=1;i<=n;i++) { for(j=1;j<=n;j++) ma[i][j]=0; ma[i][i]=1; } } void floyd() { int i,j,k; for(k=1;k<=n;k++) { for(i=1;i<=n;i++) { for(j=1;j<=n;j++) if(ma[i][j]<ma[i][k]*ma[k][j]) { ma[i][j]=ma[i][k]*ma[k][j]; } } } } int main() { char s[100],s1[100],s2[100]; int c=0; while(scanf("%d",&n)!=EOF,n) { int i,j,k,w=1; map<string,int>mm; for(i=1;i<=n;i++) { scanf("%s",s); mm[s]=i; } scanf("%d",&m); init(); for(i=0;i<m;i++) { int a,b; scanf("%s%lf%s",s1,&rate,s2); a=mm[s1]; b=mm[s2]; ma[a][b]=rate; } floyd(); for(i=1;i<=n;i++) if(ma[i][i]>1) { w=0; break; } printf("Case %d: ",++c); if(w==0) printf("Yes\n"); else printf("No\n"); } } |
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