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278. First Bad Version

https://leetcode.com/problems/first-bad-version/

Python​

class Solution:
    def firstBadVersion(self, n: int) -> int:
        l, r = 1, n
        while l <= r:
            cur = (l+r) // 2
            if isBadVersion(cur):
                r = cur - 1
            else:
                l = cur + 1

        return l

Go​

Binary Search​

func firstBadVersion(n int) int {
    left, right := 1, n

    for left <= right {
        pivot := (left+right) / 2

        if isBadVersion(pivot) {
            right = pivot - 1
        } else {
            left = pivot + 1
        }
    }
    return left
}