Description

Submission

// The API isBadVersion is defined for you.
// bool isBadVersion(int version);

class Solution {
public:
    int firstBadVersion(int n) {
        
        int l = 1;
        int r = n;
        int m = (r - l) / 2 + l;

        for(; l <= r; m = (r - l) / 2 + l) {
            if(isBadVersion(m)) {
                r = m -1;
            } else {
                l = m + 1;
            }
        }
        if(isBadVersion(min(l, r))) return min(l ,r);
        return max(l, r);
    }
};