LeetCode 278. First Bad Version

最新推荐文章于 2023-09-17 21:54:28 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错误的产品版本的方法。在一个包含多个连续开发版本的产品中，需要找到首个失败的版本以进行修复。通过实现特定的API调用并最小化其调用次数，可以快速定位到该版本。

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.

分析：本题大意就是找到第一个使 isBadVersion(version) 返回为false的索引值。本题与(M) Search Insert Position 类似

题目要求减少调用API的次数。可以选择二叉查找法。

代码：

/* 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 l = 1, r = n;
        int m;        
        while(l < r){
            m = l + (r - l) / 2;// 二叉查找
            boolean f1 = isBadVersion(m);
            if(f1) r = m;// 若当前 m 对应为假，则记录下来
            else l = m + 1;// 否则循环判断下半区
        }// 循环结束，r 一定指向第一个badVersion
        return r;
    }
}