LeetCode-in-All

136. Single Number

Easy

Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.

You must implement a solution with a linear runtime complexity and use only constant extra space.

Example 1:

Input: nums = [2,2,1]

Output: 1

Example 2:

Input: nums = [4,1,2,1,2]

Output: 4

Example 3:

Input: nums = [1]

Output: 1

Constraints:

Solution

defmodule Solution do
  @spec single_number(nums :: [integer]) :: integer
  def single_number(nums) do
    nums
    |> Enum.frequencies()
    |> Enum.find(fn {k, v} -> v == 1 end)
    |> elem(0)
  end
end