First Bad Version 二分查找

最新推荐文章于 2021-12-22 22:27:38 发布

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本文介绍了一种使用二分查找算法高效确定首次出现故障的产品版本的方法。通过最小化调用质量检查API的次数来优化搜索过程。

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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.

public class Solution extends VersionControl {

    public int firstBadVersion(int n) {
        int start=1;
        int end=n;
        int mid;
        while(start<=end){
            mid=((end-start)>>1)+start;//二分查找，这种写法不错
            //mid=(start+end)/2;//这样会溢出，所以选择写成上边那样，妙不妙
            if(isBadVersion(mid))
                end=mid-1;//注意
            else
                start=mid+1;//注意
        }
       //return end+1;//注意
       return start;//这俩都可以，因为最后循环结束时，一定有start>end且只大1
    }
}