first_bad_version.rb

# https://leetcode.com/problems/first-bad-version/
#
# You are a product manager and currently leading a team to develop a new
# product. Unfortunately, the latest version of your product fails the quality
# check. Since each version is developed based on the previous version, all
# the versions after a bad version are also bad.
#
# Suppose you have n versions [1, 2, ..., n] and you want to find out the
# first bad one, which causes all the following ones to be bad.
#
# You are given an API bool isBadVersion(version) which will return whether
# version is bad. Implement a function to find the first bad version. You
# should minimize the number of calls to the API.
#
# Credits:
#
#     Special thanks to @jianchao.li.fighter for adding this problem and
#     creating all test cases.


# The is_bad_version API is already defined for you.
# @param {Integer} version
# @return {boolean} whether the version is bad
# def is_bad_version(version):


# @param {Integer} n
# @return {Integer}
def first_bad_version(n)
  (1..n).bsearch { |i| is_bad_version(i) }
end