0167-two-sum-ii-input-array-is-sorted.rb

# frozen_string_literal: true

# 167. Two Sum II - Input Array Is Sorted
# https://leetcode.com/problems/two-sum-ii-input-array-is-sorted
# Medium

=begin
Given a 1-indexed array of integers numbers that is already sorted in non-decreasing order, find two numbers such that they add up to a specific target number. Let these two numbers be numbers[index1] and numbers[index2] where 1 <= index1 < index2 <= numbers.length.

Return the indices of the two numbers, index1 and index2, added by one as an integer array [index1, index2] of length 2.

The tests are generated such that there is exactly one solution. You may not use the same element twice.

Your solution must use only constant extra space.

Example 1:
Input: numbers = [2,7,11,15], target = 9
Output: [1,2]
Explanation: The sum of 2 and 7 is 9. Therefore, index1 = 1, index2 = 2. We return [1, 2].

Example 2:
Input: numbers = [2,3,4], target = 6
Output: [1,3]
Explanation: The sum of 2 and 4 is 6. Therefore index1 = 1, index2 = 3. We return [1, 3].

Example 3:
Input: numbers = [-1,0], target = -1
Output: [1,2]
Explanation: The sum of -1 and 0 is -1. Therefore index1 = 1, index2 = 2. We return [1, 2].

Constraints:
2 <= numbers.length <= 3 * 104
-1000 <= numbers[i] <= 1000
numbers is sorted in non-decreasing order.
-1000 <= target <= 1000
The tests are generated such that there is exactly one solution.
=end

# @param {Integer[]} numbers
# @param {Integer} target
# @return {Integer[]}
def two_sum(numbers, target)
  hash = {}

  numbers.each_with_index do |num, i|
    return hash[target - num] + 1, i + 1 if hash[target - num]
    hash[num] = i
  end
end

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

require "test/unit"
class Test_two_sum < Test::Unit::TestCase
  def test_
    assert_equal [1, 2], two_sum([2, 7, 11, 15], 9)
    assert_equal [1, 3], two_sum([2, 3, 4], 6)
    assert_equal [1, 2], two_sum([-1, 0], -1)
  end
end