Assignment

Write application which accepts incoming requests to:
POST /upload/{number}
Content-Type=text/csv

{number} = number is the sum of two numbers to be found in the input array

Application should:

• bind input to List<List>
  • Example of input data: [[11, -4, 3, 4, 3, 2], [2, 5, 5, 3, 0, 1]]
• fail-fast on invalid input(identify cases when input should be considered incorrect)
• solve 2sum problem for every row in provided csv
• respond with List[List[List[Integer]]] where elements of output list are solutions per each line of provided csv.
  • Example of response: [[[11, -4], [2, 5]], [[2,7], [11,-2]]]

2sum problem

Find all the pairs of two integers in an unsorted array that sum up to a given S.
Examples:
S=7 => [3, 5, 2, -4, 8, 11] -> [[11, -4], [2, 5]]
S=9 => [2, 7, 11, 15, 3, -2], -> [[2,7], [11,-2]]

Error Handling

In case of invalid input application should respond with a json containing details which are enough to identify what's
wrong with input:
{ "code": "wrong.input.type", "message": "..." }

Tests

Write some tests for your rest api controllers and for validation logics of 2sum problem

Solution

BTW, /upload/{number} means only one sum-to-find for the whole set of input numbers (every 'row') So, with demo purposes, I've modified the task:

• upload/{number} uses POST JSON [[11, -4, 3, 4, 3, 2], [2, 5, 5, 3, 0, 1]] finding number;
• upload/file/{number} is closer to initial task
  • single number in URL;
  • file contents is similar to described [[11, -4, 3, 4, 3, 2], [2, 5, 5, 3, 0, 1]])
• upload/csv/ is slightly closer to the real task because it
  • expects csv file;
  • csv has the sum being searched, as the first number in every row;
• Solver class (with 2 methods for file/csv uploads) is in SumSolver class and being tested separately
• Many things are hard-coded to not overthink 8-D
• But returning error codes are (just in case) extensible in ErrorTypes
• Tests show the usage and behaviour
• Play Sird router used for uploads receiving
• I rather used Tapir or Lagom for building microservices before