二分查找

二分查找

# -*- coding: utf-8 -*- # @Time : 2022/3/28 15:20 # @Author : chuqianyu # @FileName: 二分查找2.py # @Software: PyCharm # @Blog ：https://home.cnblogs.com/u/chuqianyu class Solution:     def search(self, nums: list, target: int) -> int:         # write code here         # binarySearch         kk = Solution.binarySearch(self, nums, 0, len(nums) - 1, target)         return kk       #         暴力求解     #         for i in range(len(nums)):     #             if target == nums[i]:     #                 return i     #         else:     #             return -1      #    binarySearch     def binarySearch(self, arr, m, n, x): # m,n为下标，所以n  = len(arr)-1         if n >= m:             mid = m + ((n - m) >>1)  # 等效为 mid = int(m + (n-m)/2) #int为向下取整             if arr[mid] == x:                 return mid             elif arr[mid] > x:                 return Solution.binarySearch(self, arr, m, mid - 1, x)             else:                 return Solution.binarySearch(self, arr, mid + 1, n, x)         else:             return -1  if __name__ == __main__:     print(int(3.5)) # 3向下取整     s = Solution()     x = int(input())  # 输入要查找的数     arr = list(map(int, input().strip().split()))  # 有序数组     m = 0     n = len(arr) - 1     index = s.search(arr, x)     if index != -1:         print(元素在数组中的索引为 %d % index)     else:         print(元素不在数组中)