# ---
# title: 278. First Bad Version
# id: problem278
# author: zhwang
# date: 2022-02-12
# difficulty: Easy
# categories: Binary Search
# link: <https://leetcode.com/problems/first-bad-version/description/>
# hidden: true
# ---
# 
# 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 returns whether
# `version` is bad. Implement a function to find the first bad version. You
# should minimize the number of calls to the API.
# 
# 
# 
# **Example 1:**
# 
#     
#     
#     Input: n = 5, bad = 4
#     Output: 4
#     Explanation:
#     call isBadVersion(3) -> false
#     call isBadVersion(5) -> true
#     call isBadVersion(4) -> true
#     Then 4 is the first bad version.
#     
# 
# **Example 2:**
# 
#     
#     
#     Input: n = 1, bad = 1
#     Output: 1
#     
# 
# 
# 
# **Constraints:**
# 
#   * `1 <= bad <= n <= 231 - 1`
# 
# 
## @lc code=start
using LeetCode

function first_bad_version(n::Int, is_bad_version::Function)::Int
    left, right = 1, n
    while left <= right
        mid = (left + right) >> 1
        if is_bad_version(mid)
            right = mid -1
        else
            left = mid + 1
        end
    end
    left
end

## @lc code=end

## @lc test=start
@testset "278.first-bad-version.jl" begin
    @test first_bad_version(5, i -> (i>=4)) == 4
    @test first_bad_version(1, i -> (i>=1)) == 1
    @test first_bad_version(2022, i -> (i>=1024)) ==1024
end
## @lc test=end

## @lc info=start
# link: [solution to 278](https://leetcode-cn.com/problems/first-bad-version/solution/278-di-yi-ge-cuo-wu-de-ban-ben-by-rex-rs-92ts/)
## @lc info=end