二分查找算法+代码(通俗易懂简洁扼要)♀?♀原文出处 二分查找算法+代码(通俗易懂简洁扼要)欢迎关注我知乎帐号进击的steve二分查找是一个可以把单值查找时间复杂度从O(n)降到O(logn)的算法。二分查找的前提是数组有序(按照从小到大或从大到小的顺序排列)有两种方法可以实现：递归和循环为了节约存放函数调用的栈，一般建议使用循环def binarysearch(nums, target): # 循环实现 时间复杂度O(logn) low = 0 high = len(nums)-1 while low <= high: mid = (low + high) // 2 guess = nums[mid] if guess == target: return mid elif guess < target: low = mid + 1 else: high = mid - 1 return -1如果nums=[1,2,7,7,7,7,7,9], target=7, 查找最左侧的7怎么办?def binarysearch2(self, nums, target): # 时间复杂度O(logn) left, right = 0, len(nums)-1 while left <= right: mid = (left + right) // 2 if nums[mid] == target: if mid == 0 or nums[mid-1] != target: return mid else: right = mid - 1 elif nums[mid] < target: left = mid + 1 else: right = mid - 1 return -1github代码出处：https://github.com/stevezkw19...欢迎关注我的github：https://github.com/stevezkw1998
