Leetcode题解 278. First Bad Version

最新推荐文章于 2022-02-01 16:34:00 发布

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本文介绍了一种使用二分查找算法来高效确定首次出现故障的产品版本的方法。在一个由多个连续开发的版本组成的序列中，一旦某个版本开始出现故障，之后的所有版本都将受到影响。通过调用一个特殊的API isBadVersion(version)，可以判断指定版本是否故障。目标是最小化API调用次数，快速定位到首个故障版本。

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.

二分查找

/* The isBadVersion API is defined in the parent class VersionControl.
      boolean isBadVersion(int version); */

public class Solution extends VersionControl {
    public int firstBadVersion(int n) {
        int low=1;
        int high=n;
        while(low<=high){
            int temp=low+(high-low)/2;
            if(low==high){
                return high;
            }
            else if(isBadVersion(temp)){
                high=temp;
            }else if(!isBadVersion(temp)){
                low=temp+1;
            }
        }
        return 1;
    }
}