>我在程序中获得的值为"无"?我哪里做错了?
lis2 = [1, 3, 6, 2, 5, 4, 8, 12]
lis2 = sorted(lis2)
start = 0
end = len(lis2)
mid = (start+end)/2
def binary_search(i):
global mid,start,end
if i==lis2[mid]:
return "Found"
elif i<lis2[mid]:
end = mid-1
mid = (start+end)/2
elif i>lis2[mid]:
start = mid+1
mid = (start+end)/2
else:
return "Not Found"
binary_search(i)
print(binary_search(6))
任何帮助,不胜感激。提前感谢!
存在三个错误 -
- 首先如评论中所述,也是您写的答案之一 -
binary_search(i)
而不是return binary_search(i)
- 其次是逻辑错误。如果列表中不存在元素,则代码将进入无限循环。为了避免这个检查,如果
start > end
,如果ti发生,则元素不存在。 - 第三,您将
end
初始化为len(lis2)
,如果您尝试搜索列表中不存在的元素并且大于列表中的最大元素(例如23(,这将提供IndexError: list index out of range
。所以把end = len(lis2)
改成end = len(lis2)-1
正确的代码 -
lis2 = [1, 3, 6, 2, 5, 4, 8, 12]
lis2 = sorted(lis2)
start = 0
end = len(lis2)-1
mid = int((start+end)/2)
def binary_search(i):
global mid,start,end
if(start>end):
return "Not Found"
if i==lis2[mid]:
return "Found"
elif i<lis2[mid]:
end = mid-1
mid = int((start+end)/2)
elif i>lis2[mid]:
start = mid+1
mid = int((start+end)/2)
return binary_search(i)
print(binary_search(6))
在函数的末尾,你需要在调用函数递归时返回结果:
def binary_search(i):
global mid,start,end
if i==lis2[mid]:
return "Found"
elif i<lis2[mid]:
end = mid-1
mid = (start+end)/2
elif i>lis2[mid]:
start = mid+1
mid = (start+end)/2
else:
return "Not Found"
return binary_search(i) # <----- EDITED