LeetCode笔记：278. First Bad Version

Question: （谷歌翻译）
You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed based on the previous version, all the versions after a bad version are also bad.
您是产品经理，目前领导团队开发新产品。不幸的是，您的产品的最新版本未通过质量检查。由于每个版本是基于以前的版本开发的，所有版本在坏版本后也是坏的。

Suppose you have n versions [1, 2, …, n] and you want to find out the first bad one, which causes all the following ones to be bad.
假设你有n个版本[1，2，…，n]，你想找出第一个坏的，这导致所有以下的坏。

You are given an API bool isBadVersion(version) which will return whether version is bad. Implement a function to find the first bad version. You should minimize the number of calls to the API.
你得到一个API bool isBadVersion（version），它将返回version是否是坏的。实现一个函数来找到第一个坏版本。您应该尽量减少对API的调用次数。

---

Top Solutions:
该解法**。

public int firstBadVersion(int n) {
    int start = 1, end = n;
    while (start < end) { /* or start <= end */
        int mid = start + (end-start) / 2; //直接相加可能溢出
        if (!isBadVersion(mid)) start = mid + 1;
        else end = mid; /* or end = mid - 1 */
    }        
    return start;
}

“O(lgN) simple Java solution”
https://discuss.leetcode.com/topic/26272/o-lgn-simple-java-solution

---

My Solution:

***