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The common programming challenge put to prospective hires

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Alex's toy robot

The toy robot is a simple programming exercise designed to demonstrate a basic level of programming competency, useful for screening of applicants for developer roles, you can read a bit about the motivation behind it in this post:

https://joneaves.wordpress.com/2014/07/21/toy-robot-coding-test/

Challenge

The challenge, taking from the comment in the above post, was:

Description: . The application is a simulation of a toy robot moving on a square tabletop, of dimensions 5 units x 5 units. . There are no other obstructions on the table surface. . The robot is free to roam around the surface of the table, but must be prevented from falling to destruction. Any movement that would result in the robot falling from the table must be prevented, however further valid movement commands must still be allowed.

. Create an application that can read in commands of the following form – PLACE X,Y,F MOVE LEFT RIGHT REPORT

. PLACE will put the toy robot on the table in position X,Y and facing NORTH, SOUTH, EAST or WEST. . The origin (0,0) can be considered to be the SOUTH WEST most corner. . The first valid command to the robot is a PLACE command, after that, any sequence of commands may be issued, in any order, including another PLACE command. The application should discard all commands in the sequence until a valid PLACE command has been executed. . MOVE will move the toy robot one unit forward in the direction it is currently facing. . LEFT and RIGHT will rotate the robot 90 degrees in the specified direction without changing the position of the robot. . REPORT will announce the X,Y and F of the robot. This can be in any form, but standard output is sufficient.

. A robot that is not on the table can choose the ignore the MOVE, LEFT, RIGHT and REPORT commands. . Input can be from a file, or from standard input, as the developer chooses. . Provide test data to exercise the application.

Constraints: The toy robot must not fall off the table during movement. This also includes the initial placement of the toy robot. Any move that would cause the robot to fall must be ignored.

Example Input and Output: a) PLACE 0,0,NORTH MOVE REPORT Output: 0,1,NORTH

b) PLACE 0,0,NORTH LEFT REPORT Output: 0,0,WEST

c) PLACE 1,2,EAST MOVE MOVE LEFT MOVE REPORT Output: 3,3,NORTH

Notes

  • I was called about a job and the recruiter asked if I had done this challenge. I hadn't, so I decided that it was something I should do. I never intended however to upload it to my github, thinking it should just be something to keep handy should anyone ever ask for it. On advice from another mentor I decided to upload it, but there is no evidence of git change history as a result because at the time I was viewing it as a simple challenge.
  • The rspec tests honestly were an afterthought, I didn't do them as I was coding the robot but I'm glad that I did in the end because they ended up catching a few issues and it solidified my impression of the necessity for testing.

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