1688-count-of-matches-in-tournament.rb

# frozen_string_literal: true

# 1688. Count of Matches in Tournament
# Easy
# https://leetcode.com/problems/count-of-matches-in-tournament

=begin
You are given an integer n, the number of teams in a tournament that has strange rules:
* If the current number of teams is even, each team gets paired with another team. A total of n / 2 matches are played, and n / 2 teams advance to the next round.
* If the current number of teams is odd, one team randomly advances in the tournament, and the rest gets paired. A total of (n - 1) / 2 matches are played, and (n - 1) / 2 + 1 teams advance to the next round.
Return the number of matches played in the tournament until a winner is decided.

Example 1:
Input: n = 7
Output: 6
Explanation: Details of the tournament:
- 1st Round: Teams = 7, Matches = 3, and 4 teams advance.
- 2nd Round: Teams = 4, Matches = 2, and 2 teams advance.
- 3rd Round: Teams = 2, Matches = 1, and 1 team is declared the winner.
Total number of matches = 3 + 2 + 1 = 6.

Example 2:
Input: n = 14
Output: 13
Explanation: Details of the tournament:
- 1st Round: Teams = 14, Matches = 7, and 7 teams advance.
- 2nd Round: Teams = 7, Matches = 3, and 4 teams advance.
- 3rd Round: Teams = 4, Matches = 2, and 2 teams advance.
- 4th Round: Teams = 2, Matches = 1, and 1 team is declared the winner.
Total number of matches = 7 + 3 + 2 + 1 = 13.

Constraints:
1 <= n <= 200
=end

# @param {Integer} n
# @return {Integer}
def number_of_matches(n)
  matches = 0
  teams_advancing = n

  while teams_advancing > 1 do
    matches += teams_advancing / 2
    teams_advancing = (teams_advancing / 2.0).ceil
  end

  matches
end

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

require "test/unit"
class Test_number_of_matches < Test::Unit::TestCase
  def test_
    assert_equal 6, number_of_matches(7)
    assert_equal 13, number_of_matches(14)
  end
end