Without it, they may be using information of a previous number that is not true anymore, like considering it is greater than zero when it's not anymore.

grpc-service

The goal of this project is to document the setup for establishing a gRPC communication between a server and its clients.

GuessNumber Service

Statements

• A special number is randomly generated at the server startup
  • It gets updated every time a guess is made by a client with the exact same number
• For each guess, the server will respond with
  • < if given number is less than special number
  • > if given number is greater than special number
  • = if given number is equal to special number
    • There will also be a locked box as your prize
• Guessed numbers must lie within the interval defined by: $[-8 * 10^{18}, +8 * 10^{18}]$
  • Every number with up to $18$ digits
  • Given that your computer probably can't process more than $10^{10}$ operations in a second, a naive approach of guessing each possible number would take at least $5$ years to execute
• There is in fact one algorithm capable of solving this question a bit faster - binary search
  • Instead of guessing each number, you can benefit from the server response to avoid making unnecessary guesses
  • Since each wrong guess reduces the amount of possibilities by its half
    • Worst case goes from $O(N)$ to $O(log_2(N))$
      • $N$ is the amount of possible values: $\approx 16 * 10^{18}$
        • which also happens to be quite close to the amount of possible numbers to fit inside a 64-bit integer: $log_2(16 * 10^{18}) \approxeq 64$

Protocol Buffers

There are two defined procedures to be remotely called

• GuessRandomNumber
  • Input: Guess
  • Output: GuessResponse
• OpenBox
  • Input: LockedBox
  • Output: Box

Check it out!

Programming Languages

1. Go

• LockedPandoraBox must have encrypted message
• OpenBox decrypts and output as OpenedPandoraBox