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JaeHyoLee's solution

to Isogram in the Lua Track

Published at Jul 13 2018 · 0 comments
Instructions
Test suite
Solution

Determine if a word or phrase is an isogram.

An isogram (also known as a "nonpattern word") is a word or phrase without a repeating letter, however spaces and hyphens are allowed to appear multiple times.

Examples of isograms:

  • lumberjacks
  • background
  • downstream
  • six-year-old

The word isograms, however, is not an isogram, because the s repeats.

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

Wikipedia https://en.wikipedia.org/wiki/Isogram

Submitting Incomplete Solutions

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

isogram_spec.lua

local is_isogram = require 'isogram'

describe('isogram', function()
  it('should identify simple isograms', function()
    assert.is_true(is_isogram('duplicates'))
    assert.is_true(is_isogram('subdermatoglyphic'))
  end)

  it('should identify words with repeated letters as non-isograms', function()
    assert.is_false(is_isogram('eleven'))
  end)

  it('should be case insensitive', function()
    assert.is_false(is_isogram('Alphabet'))
  end)

  it('should allow punctuations in isograms', function()
    assert.is_true(is_isogram('thumbscrew-japingly'))
  end)

  it('should allow repeated punctuation in isograms', function()
    assert.is_true(is_isogram('Hjelmqvist-Gryb-Zock-Pfund-Wax'))
  end)

  it('should identify non-isogram sentences', function()
    assert.is_false(is_isogram('the quick brown fox'))
  end)

  it('should identify isogram sentences', function()
    assert.is_true(is_isogram('Emily Jung Schwartzkopf'))
  end)
end)
return function(s)
  local n = s:gsub('%A',''):lower()
  local t = table.pack(n:byte(1, #n))
  table.sort(t)

  for k = 2, #t do
    if t[k - 1] == t[k] then return false end
  end
  return true
end

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