Pro.ID21059 TitleExchange Rates Title链接http://10.20.2.8/oj/exercise/problem?problem_id=21059 AC0 Submit698 Ratio0.00% 时间&空间限制描述Using money to pay for goods and services usually makes life easier, but sometimes people prefer to trade items directly without any money changing hands. In order to ensure a consistent "price", traders set an exchange rate between items. The exchange rate between two items A and B is expressed as two positive integers m and n, and says that m of item A is worth n of item B. For example, 2 stoves might be worth 3 refrigerators. (Mathematically, 1 stove is worth 1.5 refrigerators, but since it's hard to find half a refrigerator, exchange rates are always expressed using integers.) Your job is to write a program that, given a list of exchange rates, calculates the exchange rate between any two items. 输入The input contains one or more commands, followed by a line beginning with a period that signals the end of the file. Each command is on a line by itself and is either an assertion or a query. An assertion begins with an exclamation point and has the format ! m itema = n itemb where itema and itemb are distinct item names and m and n are both positive integers less than 100. This command says that m of itema are worth n of itemb. A query begins with a question mark, is of the form ? itema = itemb and asks for the exchange rate between itema and itemb, where itema and itemb are distinct items that have both appeared in previous assertions (although not necessarily the same assertion). 输出Description Using money to pay for goods and services usually makes life easier, but sometimes people prefer to trade items directly without any money changing hands. In order to ensure a consistent "price", traders set an exchange rate between items. The exchange rate between two items A and B is expressed as two positive integers m and n, and says that m of item A is worth n of item B. For example, 2 stoves might be worth 3 refrigerators. (Mathematically, 1 stove is worth 1.5 refrigerators, but since it's hard to find half a refrigerator, exchange rates are always expressed using integers.) Your job is to write a program that, given a list of exchange rates, calculates the exchange rate between any two items. Input The input contains one or more commands, followed by a line beginning with a period that signals the end of the file. Each command is on a line by itself and is either an assertion or a query. An assertion begins with an exclamation point and has the format ! m itema = n itemb where itema and itemb are distinct item names and m and n are both positive integers less than 100. This command says that m of itema are worth n of itemb. A query begins with a question mark, is of the form ? itema = itemb and asks for the exchange rate between itema and itemb, where itema and itemb are distinct items that have both appeared in previous assertions (although not necessarily the same assertion). Output For each query, output the exchange rate between itema and itemb based on all the assertions made up to that point. Exchange rates must be in integers and must be reduced to lowest terms. If no exchange rate can be determined at that point, use question marks instead of integers. Format all output exactly as shown in the example. Note:
Sample Input ! 6 shirt = 15 sock
! 47 underwear = 9 pant
? sock = shirt
? shirt = pant
! 2 sock = 1 underwear
? pant = shirt
.Sample Output 5 sock = 2 shirt
? shirt = ? pant
45 pant = 188 shirtSource 样例输入! 6 shirt = 15 sock
! 47 underwear = 9 pant
? sock = shirt
? shirt = pant
! 2 sock = 1 underwear
? pant = shirt
.样例输出5 sock = 2 shirt
? shirt = ? pant
45 pant = 188 shirt作者 |
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