谁能告诉我这个二进制搜索代码哪里出错了？无法向用户打印索引

Question

def binarySearch(list, selection):
  start = 0
  end = len(list) - 1

  while start <= end:
    middle = start + (end - start) // 2  
    middleValue = list[middle]
    if middleValue == selection:
      return middle
    elif selection < middleValue:
      end = middle - 1
    else:
      start = middle + 1

  return None

lista = [1, 5, 7, 10, 11, 19,]

print(lista)

selectiona = int(input('Enter a number to search for: '))
index = lista.index(selectiona)

binarySearch(lista, selectiona)


print(str(selectiona)) + "found at index " + str(index))

exit = input()

它可以在不打印索引的情况下工作，但这是一个要求。如果有人可以就我做错的事情提出建议，我将不胜感激。谢谢

Answer 1

在print(str(selectiona)) + "found at index " + str(index)) 行中你的括号是错误的，你在selectiona 之后关闭了太多。试试这个：

print(str(selectiona) + "found at index " + str(index))

此外，二进制搜索的结果不是您要打印的结果。你的意思是改用index = binarySearch(lista, selectiona) 吗？

Answer 2

您正在使用index = lista.index(selectiona) 行中的python 模块获取index，并且您没有使用binarySearch 函数提供的输出。

def binarySearch(list, selection):
  start = 0
  end = len(list) - 1

  while start <= end:
    middle = start + (end - start) / 2  
    middleValue = list[middle]
    if middleValue == selection:
      return middle
    elif selection < middleValue:
      end = middle - 1
    else:
      start = middle + 1

  return None

lista = [1, 5, 7, 10, 11, 19,]

print(lista)

selectiona = int(input('Enter a number to search for: '))

index = binarySearch(lista, selectiona)

if index:
    print(str(selectiona) + " found at index " + str(index))
else:
    print(str(selectiona) + " is not there in the list")

exit = input()