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to Sum Of Multiples in the Lua Track

Published at Jul 13 2018 · 0 comments
Test suite

Given a number, find the sum of all the unique multiples of particular numbers up to but not including that number.

If we list all the natural numbers below 20 that are multiples of 3 or 5, we get 3, 5, 6, 9, 10, 12, 15, and 18.

The sum of these multiples is 78.

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.


A variation on Problem 1 at Project Euler http://projecteuler.net/problem=1

Submitting Incomplete Solutions

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


local sum_of_multiples = require('sum-of-multiples')

describe('sum-of-multiples', function()
  it('should sum multiples of a single number', function()
    assert.same(9, sum_of_multiples({ 3 }).to(7))
    assert.same(15, sum_of_multiples({ 5 }).to(12))

  it('should sum multiples of a list of numbers', function()
    assert.same(33, sum_of_multiples({ 3, 5 }).to(11))
    assert.same(129, sum_of_multiples({ 7, 3 }).to(25))
    assert.same(153, sum_of_multiples({ 7, 3, 8 }).to(25))

  it('should calculate multiples up to, but not including, the limit', function()
    assert.same(9, sum_of_multiples({ 3 }).to(9))
    assert.same(23, sum_of_multiples({ 3, 5 }).to(10))

  it('should not include a multiple more than once', function()
    assert.same(35, sum_of_multiples({ 2, 5 }).to(11))
    assert.same(sum_of_multiples({ 2 }).to(11), sum_of_multiples({ 2, 4 }).to(11))
return function(input)

  local input = input or { 3, 5 }
  local elements = {}
  local sum = 0

  local function to(end_number)
    for _, value in ipairs(input) do
      for i = 1, end_number do
        if i * value < end_number then elements[i * value] = true
        else break end

    for key, _ in pairs(elements) do
      sum = sum + key
    return sum

  return {to = to}

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