I tried set() function and to my surprise it didn't work here. I know it is a little cheating here but it definitely gives you the right answer. Can anyone tell me why set() doesn't work for this question. Thanks much.
I used set() in Python but it didn't work

I also encountered this kind of situation.
Then I see the requirement: 'Your function should return length = 2, and A is now [1,2].'
After use set() function, the A is also [1, 1, 2], it doesn't match the requirement.Then I tried the code below to modify A after use set() function. And it works.
class Solution: # @param a list of integers # @return an integer def removeDuplicates(self, A): new = sorted(list(set(A))) length = len(new) for i in xrange(length): A[i] = new[i] return length
PS: use A = sorted(list(set(A))) also doesn't work.