2300-successful-pairs-of-spells-and-potions.rb

# frozen_string_literal: true

# 2300. Successful Pairs of Spells and Potions
# https://leetcode.com/problems/successful-pairs-of-spells-and-potions
# Medium

=begin

You are given two positive integer arrays spells and potions, of length n and m respectively, where spells[i] represents the strength of the ith spell and potions[j] represents the strength of the jth potion.

You are also given an integer success. A spell and potion pair is considered successful if the product of their strengths is at least success.

Return an integer array pairs of length n where pairs[i] is the number of potions that will form a successful pair with the ith spell.

### Example 1:
Input: spells = [5,1,3], potions = [1,2,3,4,5], success = 7
Output: [4,0,3]
Explanation:
- 0th spell: 5 * [1,2,3,4,5] = [5,10,15,20,25]. 4 pairs are successful.
- 1st spell: 1 * [1,2,3,4,5] = [1,2,3,4,5]. 0 pairs are successful.
- 2nd spell: 3 * [1,2,3,4,5] = [3,6,9,12,15]. 3 pairs are successful.
Thus, [4,0,3] is returned.

### Example 2:
Input: spells = [3,1,2], potions = [8,5,8], success = 16
Output: [2,0,2]
Explanation:
- 0th spell: 3 * [8,5,8] = [24,15,24]. 2 pairs are successful.
- 1st spell: 1 * [8,5,8] = [8,5,8]. 0 pairs are successful.
- 2nd spell: 2 * [8,5,8] = [16,10,16]. 2 pairs are successful.
Thus, [2,0,2] is returned.

### Constraints:
* n == spells.length
* m == potions.length
* 1 <= n, m <= 105
* 1 <= spells[i], potions[i] <= 105
* 1 <= success <= 1010
=end

# @param {Integer[]} spells
# @param {Integer[]} potions
# @param {Integer} success
# @return {Integer[]}
def successful_pairs(spells, potions, success)
  potions.sort!
  spells.map do |spell_str|
    min_pot_str = success.fdiv(spell_str)
    idx = potions.bsearch_index { |potion| potion >= min_pot_str }
    idx.nil? ? 0 : potions.size - idx
  end
end

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

require "test/unit"
class Test_successful_pairs < Test::Unit::TestCase
  def test_
    assert_equal [4, 0, 3], successful_pairs([5, 1, 3], [1, 2, 3, 4, 5], 7)
    assert_equal [2, 0, 2], successful_pairs([3, 1, 2], [8, 5, 8], 16)
  end
end