First Bad Version

最新推荐文章于 2025-08-22 15:34:07 发布

原创最新推荐文章于 2025-08-22 15:34:07 发布 · 261 阅读

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本文介绍了一个使用二分搜索算法来高效查找首个错误版本的代码实现。通过定义一个接口 isBadVersion 来判断某个版本是否为错误版本，并利用该接口在 O(log n) 时间复杂度内找到首个错误版本。

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c++

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

class Solution {
public:
    int firstBadVersion(int n) {
        if (n == 1)
            return n;
        int left = 1, right = n;
        while (left < right) {
            int mid = left + (right - left) / 2;
            if (isBadVersion(mid))
                right = mid - 1;
            else
                left = mid + 1;
        }
        return isBadVersion(left) ? left : left + 1;
    }
};

python

# The isBadVersion API is already defined for you.
# @param version, an integer
# @return a bool
# def isBadVersion(version):

class Solution(object):
    def firstBadVersion(self, n):
        """
        :type n: int
        :rtype: int
        """
        if n==1:
            return n;
        left,right =1,n

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

        return left if isBadVersion(left) else left+1