[278]First Bad Version

最新推荐文章于 2024-11-06 09:58:18 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。在一个包含多个连续开发版本的产品中，需要找到第一个引入故障的版本。通过实现特定API调用，此算法能够最小化检查版本所需的操作次数。

【题目描述】

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.

【思路】

就是一道二分查找的题目，要注意的一点是(low+high)/2的时候可能会溢出，所以要改写成low+(high-low)/2.所以说代码真的很神奇呀~

【代码】

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

class Solution {
public:
    int firstBadVersion(int n) {
      int low=1;
      int high=n;
      while(low<=high){
          int middle=low + ( high - low ) / 2;
          if(isBadVersion(middle)==true&&isBadVersion(middle-1)==false) return middle;
          if(isBadVersion(middle)==true&&isBadVersion(middle-1)==true) high=middle-1;
          if(isBadVersion(middle)==false) low=middle+1;
      }
    }
};