.. _leetcode-0278:

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:badge:`EASY,badge-info` 0278. First Bad Version
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Problem Statement
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`Leetcode Link <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 returns whether version
is bad. Implement a function to find the first bad version. You should minimize
the number of calls to the API.

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Examples
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**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.

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Constraints
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``1 <= bad <= n <= 231 - 1``

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Solution
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This is *similar* to a binary search.


.. literalinclude:: solution.py
    :caption: Solution
    :linenos:
    :language: python