278 第一个错误的版本

https://leetcode.cn/leetbook/read/top-interview-questions-easy/xnto1s/

https://leetcode.cn/problems/first-bad-version/description/

cost: 6m52s

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

class Solution {
public:
    int firstBadVersion(int n) {
        if (isBadVersion(1)) {
            return 1;
        }
        int left = 1, right = n;
        while (left < right) {
            if (left == right - 1) {
                return right;
            }
            int mid = left + (right - left) / 2;
            bool bad = isBadVersion(mid);
            if (bad) {
                right = mid;
            } else {
                left = mid;
            }
        }
        return -1;
    }
};

• 时间复杂度：O(log(n))
• 空间复杂度：O(1)