Python(二分法查找)

• 大饼找芝麻(二分法查找)

•  二分法针对的对象要是有序的队列,通过索引找到你要查找的值
•  思想:取一个索引开头left,取一个索引末尾(len(队列)-1)right,让你的值跟(left + right)//2(middle)比
• 如果索引middle值比你查的值大,把middle赋值给right,反之把middle赋值给left;
• 代码展示:

• lst = [11,22,33,44,55,66,77,88,99,123,234,345,456,567,678,789,1111]
  n = 456
  left = 0
  right = len(lst) - 1
  count = 1
  while left <= right:
      middle = (left + right) // 2
      if n > lst[middle]:
          left = middle + 1
      elif n < lst[middle]:
          right = middle - 1
      else:
          print('查找次数%s' % count)
          print("存在位置%s" % middle)
          break
      count = count + 1
  else:
      print("不存在")

  用递归方法实现二分法:

• def binary_search(left, right, n):
      middle = (left + right)//2
      if left > right:
          return -1
      if n > lst[middle]:
          left = middle + 1
      elif n < lst[middle]:
          right = middle - 1
      else:
          return middle
      return binary_search(left, right, n)
  print(binary_search(0, len(lst)-1, 65) )