1046-last-stone-weight.rb

# frozen_string_literal: true

# 1046. Last Stone Weight
# https://leetcode.com/problems/last-stone-weight

=begin

You are given an array of integers stones where stones[i] is the weight of the ith stone.

We are playing a game with the stones. On each turn, we choose the heaviest two stones and smash them together. Suppose the heaviest two stones have weights x and y with x <= y. The result of this smash is:

If x == y, both stones are destroyed, and
If x != y, the stone of weight x is destroyed, and the stone of weight y has new weight y - x.
At the end of the game, there is at most one stone left.

Return the weight of the last remaining stone. If there are no stones left, return 0.

### Example 1:
Input: stones = [2,7,4,1,8,1]
Output: 1
Explanation:
We combine 7 and 8 to get 1 so the array converts to [2,4,1,1,1] then,
we combine 2 and 4 to get 2 so the array converts to [2,1,1,1] then,
we combine 2 and 1 to get 1 so the array converts to [1,1,1] then,
we combine 1 and 1 to get 0 so the array converts to [1] then that's the value of the last stone.

### Example 2:
Input: stones = [1]
Output: 1

### Constraints:
* 1 <= stones.length <= 30
* 1 <= stones[i] <= 1000

=end

# @param {Integer[]} stones
# @return {Integer}
def last_stone_weight(stones)
  while stones.size > 1
    stones.sort!
    a, b = stones.pop(2)
    stones.push(b - a) if b - a > 0
  end
  stones.empty? ? 0 : stones.first
end

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

require "test/unit"
class Test_last_stone_weight < Test::Unit::TestCase
  def test_
    assert_equal 1, last_stone_weight([2, 7, 4, 1, 8, 1])
    assert_equal 1, last_stone_weight([1])
  end
end