first_bad_version.cpp

class Solution {
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;
    }
};