First Bad Version Solutions in C++

// Source : https://leetcode.com/problems/first-bad-version/
// Author : Hao Chen
// Date   : 2015-10-19



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

class Solution {
public:
    //Binary search
    int firstBadVersion(int n) {
        int low=1, high=n;
        while(low <= high) {
            int mid = low + (high - low)/2;
            if (isBadVersion(mid) && !isBadVersion(mid-1)){
                return mid;
            }
            if (isBadVersion(mid)) {
                high = mid - 1;
            }else{
                low = mid + 1;
            }
        }
        return -1;
    }
};