问题描述
我已经在Python做了一个合并排序程序，它是完全运行，但我已经修改了它算参与反转的数目，现在是给我的错误：
I have made a merge sort program in Python and it is running perfectly but I have modified it to count the number of inversions involved and now it is giving me an error :
下面是我的code：
def merge_list(left,right,c):
result=[]
i,j=0,0
while i < len(left) and j < len(right):
if left[i] < right[j]:
result.append(left[i])
print "Left result",result
i=i+1
elif left[i] > right[j]:
result.append(right[j])
print "Right result",result
j=j+1
if right[j] < left[i] and i<j:
c=c+1
result=result+left[i:]
result=result+right[j:]
print "Inversions: ",c
return result,c
def sort_and_count(lis,count):
if len(lis)<2:
return lis
middle=len(lis) / 2
left,c1=sort_and_count(lis[:middle],count)
print "left",left
right,c2=sort_and_count(lis[middle:],count)
print "right",right
m,c=merge_list(left,right,count)
c=c+c1+c2
return m,c
if __name__=="__main__":
print "Enter 6 elements: "
i=0;lis=[];merge_lis=[];inv=0
while i<=5:
x=int(raw_input())
lis.append(x)
i=i+1
count=0
merge_lis,inv=sort_and_count(lis,count)
print "Sorted list is: ",merge_lis,inv
和我回溯：
Traceback (most recent call last):
File "Sort_and_count.py", line 53, in <module>
merge_lis,inv=sort_and_count(lis,count)
File "Sort_and_count.py", line 31, in sort_and_count
left,c1=sort_and_count(lis[:middle],count)
File "Sort_and_count.py", line 31, in sort_and_count
left,c1=sort_and_count(lis[:middle],count)
ValueError: need more than 1 value to unpack
我要去哪里错了这种方法？
Where am I going wrong with this approach?
推荐答案
这行：
return lis
这是一个问题，因为你期待 sort_and_count 返回包含两个值的元组，所以当它仅返回一个值，你必须在元组拆包的问题如系留，C1 = sort_and_count（LIS [：中]，计数）。此行应返回两个值，这样的方法的最后一行：
This is a problem, because you are expecting sort_and_count to return a tuple containing two values, so when it returns only one value you have a problem with the tuple unpacking in lines like left,c1=sort_and_count(lis[:middle],count). This line should return two values, like the last line of that method:
return m,c
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