(二分查找 拓展) leetcode278. First Bad Version

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.

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.

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.

Example:

Given n = 5, and version = 4 is the first bad version.

call isBadVersion(3) -> false
call isBadVersion(5) -> true
call isBadVersion(4) -> true

Then 4 is the first bad version.

-----------------------------------------------------------------------------------------------------

emmm，这个题就是说的是查找第一个坏了的产品。。。。用O(n)是不行的，会超时。
C++代码：

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

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;  //这个就是说的是当找到了查找到的是坏了的，但是并不一定是第一个坏了的，不过它的后面可以忽略，因为不是第一个坏了的。
            else
                left = mid + 1; //这个查找的是好的，不过前面和它自己可以忽略掉，因为不是第一个坏了的。
        }
        return left;
    }
};

官方题解：https://leetcode.com/articles/first-bad-version/