First Bad Version

最新推荐文章于 2024-11-06 09:58:18 发布

爱折腾的猫

最新推荐文章于 2024-11-06 09:58:18 发布

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分类专栏： LeetCode C/C++ 文章标签： leetcode c++ 算法

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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。在一个包含多个连续开发版本的产品中，需要找到导致后续版本均出现故障的首个坏版本。通过实现特定的API调用，可以在最少的尝试次数内定位到该版本。

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原题：
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.

解题：
解题的话比较简单，直接用二分就可以，但是需要找到第一次出现bad的元素的下标。在求取mid的时候需要用mid = left + (right - left) / 2,而不是mid=(left + right) / 2这种形式。
可以AC的C++代码如下：

bool isBadVersion(int version);

int firstBadVersion(int n) {
    int left = 1, right = n;
    int mid = 0;

    while(left < right){
        mid = left + (right - left)/2;
        if(isBadVersion(mid)) {
            right = mid;
        }else{
            left = mid + 1;
        }
    }

    if(isBadVersion(left)) 
        return left;

    return 0;
}