算法图解书籍第一章算法简介读书笔记

1. 二分查找算法的复杂度最多为:    对数是幂运算的逆运算
2. 仅当列表是有序的时候,二分查找才管用.
3. 算法的速度指的并非时间,而是操作数的增速

• 二分查找法python版本

• def binary_search(list,  item):
      low = 0
      high = len(list)-1
      while low <= high:
          # mid = int((low + high)/2)
          mid = (low + high)//2
          guess = list[mid]
          if guess == item:
              return mid
          if guess > item:
              high = mid -1
          else:
              low = mid + 1
      return None
  my_list = [1, 3, 5, 7, 9]
  print(binary_search(my_list, 3))
  print(binary_search(my_list, -1))