0136-single-number.rb

# frozen_string_literal: true

# 136. Single Number
# https://leetcode.com/problems/single-number
# Easy

=begin
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:
1 <= nums.length <= 3 * 104
-3 * 104 <= nums[i] <= 3 * 104
Each element in the array appears twice except for one element which appears only once.
=end

# @param {Integer[]} nums
# @return {Integer}
def single_number(nums)
  nums.reduce(&:^)
end

# ********************#
#       TEST         #
# ********************#

require "test/unit"
class Test_single_number < Test::Unit::TestCase
  def test_
    assert_equal 1, single_number([2, 2, 1])
    assert_equal 4, single_number([4, 1, 2, 1, 2])
    assert_equal 1, single_number([1])
  end
end