FaceBull¶
Facebook’s Chemical Industry Applications lab has been researching new ways to provide chemical stimulants to keep its engineers productive and awake. Research has isolated a series of chemical compounds when present together in sugar water, are the active ingredients of the next iteration of super-energy drink.
These chemical compounds are similar, any one compound can be used in a chemical reaction to create any other compound. Although the actual chemical reaction is negligibly cheap to cause, it requires specific expensive machinery (and catalysts) for each reaction. Machinery is specifically tailored to take one compound, and convert it into a different compound. Each machine has a purchase cost, a starting compound, and the final compound it produces. Facebook’s lab must acquire enough machinery to ensure it can create all the necessary compounds no matter what compounds are available on the market.
Write a program that takes a single argument on the command line. This argument must be a file name, which contains the input data. The program should output to standard out the cheapest way Facebook can produce its drink from any source compound or compounds (see below for output details). All chemicals mentioned in the machine catalog are assumed to be necessary for production of the drink. The catalog does not guarantee that any particular one-step reaction is possible, but it is guaranteed to have a way to transform any given compound into any other. Your submission and code solution must follow the input and output specifications below or it will be disqualified. Your program will be tested against several machine catalogs, each with different data. Additionally, your program must be fast, and give a correct answer within a matter of minutes.
Input specifications¶
The input file will contain a catalogue of available machinery. Each line of the file represents a particular machine model. The format of each line is:
<machine name> <orig compound> <new compound> <price>
Machine names start with the character ‘M’ (without the quotes) and then a non-zero padded integer. Examples of machine names are ‘M1’, ‘M2’, ‘M13’, etc.
Compound names start with the character ‘C’ (without the quotes) and then a non-zero padded integer. Examples of compound names are ‘C4’, ‘C6’, ‘C24’, etc.
Prices are simply non-zero padded integers with no commas or periods or unit designations (assume all prices are in USD). Examples of prices are ‘987334’, ‘13948295’, etc.
Each field in the input file is white space separated using spaces or tab characters. There may or may not be additional white space after the last line of entries. You are guaranteed your program will run against input files that are well formed.
Example input file:
M1 C1 C2 277317
M2 C2 C1 26247
M3 C1 C3 478726
M4 C3 C1 930382
M5 C2 C3 370287
M6 C3 C2 112344
Output specifications¶
Your output must be exactly the following. Your program must first output the sum price of all the machines to be purchased (do not insert commas, periods, or any units) as a simple integer, followed by a new line.
Your program should then output the numbers of the machines purchased in ascending order, but omitting the ‘M’ designations. Each machine number must be separated by a single space character. There should be no additional space character after the last machine. Instead, the program should output a new line after the last machine number.
Example output (there should be a newline at the end of each line):
617317
2 3 6