My accepted python code via while loop

• ``````class Solution:
# @param a list of integers
# @return an integer

def removeDuplicates(self, A):
if not A:
return 0
else:
ii,jj=1,1
while jj<len(A):
if A[ii-1]!=A[jj]:
A[ii]=A[jj]
ii+=1
jj+=1
return ii
``````

the code use a while loop with two indexes ii and jj. jj went through all elements in A and ii is used to record non-duplicated elements in A. Any comments would be appreciated

• ``````class Solution:
# @param a list of integers
# @return an integer
def removeDuplicates(self, A):
if A == []:
return(0)
count = 1;
for i in range(1,len(A)):
if A[i] != A[i-1]:
count += 1
return(count)
``````

can you help me to check why my solution is wrong?

• I don't understand why this code works with an input like A=[1,1,1]. It didn't change A to [1], but this is required, right?

• Hi chanvee,
In your code you counted all different numbers. However you forget to delete the duplicate elements in A.

• For your specific case A=[1,1,1], the code does not change matrix A at all. However the return value is 1 which determines the length of unduplicated parts in A.

• I think the point is that the grader doesn't care about changing the whole A, but only the first n items (where n is the resulting length). So it returns something like A[:n]. Which is in fact rather effective: you don't bother changing the size of the array which is computationally expensive.

• Thanks for sharing your solution! The question should probably be modified if only the first n items in the array are examined, since it specifies that they should be removed, and for Python at least lists don't work like C arrays where the length is only stipulative.

• Thanks for your sharing! I tried your solution. input: nums = [1, 1, 1, 2, 1, 1, 2], output: 4, [1, 2, 1, 2, 1, 1, 2]. It should be 2 instead of 4, yes?
I am not good at two pointers problem. Thanks!

• Hi Sen5, It seems for this problem, the given array is sorted. For your test case, this algorithm is not appropriate. Let me know if you have any additional questions.

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