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#!/usr/bin/env elixir
defmodule PWC do
@doc """
Helper function that accepts a list and generates a Multiset/
Bag implemented as a Map.
https://en.wikipedia.org/wiki/Multiset
"""
def makeBag(list) do
{_, bag} = Enum.map_reduce(list, %{}, fn i, bag ->
{ i, Map.put(bag, i, Map.get(bag, i, 0) + 1) }
end)
bag
end
@doc """
You are given an array of integers where every element
appears more than once except one element.
Find the one element that appears exactly one time.
"""
def uniqueNumber(ints) do
keys = ints
|> makeBag
|> Map.filter(fn {_, v} -> v == 1 end) # keys that occur once
|> Map.keys # return just the keys from the map
cond do
Kernel.length(keys) == 0 ->
"no element appears only once"
Kernel.length(keys) > 1 ->
"multiple elements appear only once"
true ->
keys |> List.first |> to_string
end
end
@doc """
Function to print the input, invoke the solution code,
and print the output.
"""
def solution(ints) do
IO.puts("Input: @ints = (" <> Enum.join(ints, ", ") <> ")")
IO.puts("Output: " <> uniqueNumber(ints) )
end
end
IO.puts("Example 1:")
PWC.solution([3, 3, 1])
IO.puts("\nExample 2:")
PWC.solution([3, 2, 4, 2, 4])
IO.puts("\nExample 3:")
PWC.solution([1])
IO.puts("\nExample 4:")
PWC.solution([4, 3, 1, 1, 1, 4])
IO.puts("\nInvalid Input 1 (no element appears only once):")
PWC.solution([4, 1, 1, 1, 4])
IO.puts("\nInvalid Input 2 (multiple elements appear only once):")
PWC.solution([1, 2, 3, 4])
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