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.

**Example:**

```
Given n = 5, and version = 4 is the first bad version.
``````
call isBadVersion(3) -> false
call isBadVersion(5) -> true
call isBadVersion(4) -> true
Then 4 is the first bad version
```

## Solution

Binary Search Approach

/* The isBadVersion API is defined in the parent class VersionControl. boolean isBadVersion(int version); */ public class Solution extends VersionControl { public int firstBadVersion(int n) { int left = 1; int right = n; while (left < right) { int mid = left + (right - left) / 2; if (isBadVersion(mid)) { right = mid; } else { left = mid + 1; } } return left; } }

Time Complexity: O(logn)

Space Complexity: O(1)