JaeHyoLee's solution to Series on the Lua track

Instructions

Test suite

Solution

Given a string of digits, output all the contiguous substrings of length n in that string.

For example, the string "49142" has the following 3-digit series:

And the following 4-digit series:

4914
9142

And if you ask for a 6-digit series from a 5-digit string, you deserve whatever you get.

Note that these series are only required to occupy adjacent positions in the input; the digits need not be numerically consecutive.

Running the tests

To run the tests, run the command busted from within the exercise directory.

Further information

For more detailed information about the Lua track, including how to get help if you're having trouble, please visit the exercism.io Lua language page.

Source

A subset of the Problem 8 at Project Euler http://projecteuler.net/problem=8

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

series_spec.lua

local series = require('series')

describe('series', function()
  it('should generate 1 character series', function()
    local result = {}
    for s in series('abcde', 1) do
      table.insert(result, s)
    end
    assert.same({ 'a', 'b', 'c', 'd', 'e' }, result)
  end)

  it('should generate multi-character series', function()
    local result = {}
    for s in series('hello', 3) do
      table.insert(result, s)
    end
    assert.same({ 'hel', 'ell', 'llo' }, result)
  end)

  it('should generate one series when the series length equals the string length', function()
    local result = {}
    for s in series('exercism', 8) do
      table.insert(result, s)
    end
    assert.same({ 'exercism' }, result)
  end)

  it('should return no series when the series length requested is longer than the string', function()
    local result = {}
    for s in series('1234', 5) do
      table.insert(result, s)
    end
    assert.same({}, result)
  end)
end)

return function (a, n)
  return coroutine.wrap(function()
    for i=1, #a-n+1 do
      coroutine.yield(a:sub(i, i+n-1))
    end
  end)
end

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JaeHyoLee's solution

to Series in the Lua Track