how to design a algorithm to delete the duplicated 2D points in a points list in python

Question

I have a 2D point list like:

points_list = [[2,1],[3,1],[2,1],[2,2],[2,1],[2,2]]

I want to find the duplicated 2D points, and only leave one copy of each duplicated point in the list. Such that to get a result like:

result_list = [[2,1],[3,1],[2,2]]

I know a stupid method to solve the problem, but cannot find a elegant way. Hoping someone could provide some easy ways. Thanks!

You know a stupid method? what would that be? You need to show some effort at the problem if you would like anyone to help you... — Alex Zywicki, May 29 '17 at 22:29
I'm guessing the "stupid" method the OP is talking about is a for loop in a for loop ( O(n^2) ). — SiggiSv, May 29 '17 at 22:35
yes,the stupid method I mean is Multi - for loop @ Alex Zywicki, another one method somebody told me is change the point to tuple like (2,1), then use : a = set([(2,1),(3,1),(2,1),(2,2),(2,1),(2,2)]), print(a) will get the result — Diao Lin, May 30 '17 at 06:55

Vivick · Answer 1 · 2017-05-29T22:55:41.967

-1

Here's a webpage that enumerates many possible ways of doing it (I'd go for the 4th one) :

Therefore, quoted from the link above :

def noDuplicates(seq):
    # order preserving 
    noDupes = [] 
    [noDupes.append(i) for i in seq if not noDupes.count(i)]
    return noDupes

edited May 29 '17 at 22:55

answered May 29 '17 at 22:34

Vivick

Not a "link-only answer" anymore – Vivick May 29 '17 at 22:57
Yes, but it uses a list comprehension with a side effect (very bad form), and uses `.count`. this is a very inefficient approach since `.count` iterates the whole list making the overall solution quadratic time. – juanpa.arrivillaga May 29 '17 at 23:29

1 Answers1