LeetCode 278 First Bad Version

LeetCode  278 First Bad Version

// Forward declaration of isBadVersion API.
bool isBadVersion(int version);

int firstBadVersion(int n) {
    int start=1, end=n;
    while(start < end)
    {
        int mid=start+(end-start)/2;
        if(isBadVersion(mid))
            end=mid;
        else
            start=mid+1;
    }
    return start;
}