compare two vector Python

Question

If I have for example two vectors a and b,

a = [1, 3, 6]
b = [3, 1, 6]

since the content of the vectors is the same, is it possible in some way to compare them and get true as a result?

Check [link](https://stackoverflow.com/questions/9623114/check-if-two-unordered-lists-are-equal) — Rohit-Pandey, Nov 01 '18 at 17:01
I can not use 'sort' because in reality I have to compare only one piece of vectors. my mistake because I have not explained my problem well, I wanted to avoid not to complicate the question — Dumitru Galbura, Nov 01 '18 at 17:02

score 2 · Answer 1 · answered Nov 01 '18 at 16:51

2

You can use collections.Counter:

from collections import Counter
Counter(a) == Counter(b)

answered Nov 01 '18 at 16:51

blhsing

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thank you, with this it works – Dumitru Galbura Nov 01 '18 at 17:00

Sheldore · Answer 2 · 2018-11-01T17:04:33.900

1

You can use sorted and then compare. As pointed out by blhsing, this is O(n log n) operation whereas the solution with Counter is O(n). Since n=3 in your case, the difference will be negligible but the difference will become apparent for large n. You might be interested in knowing this.

a = [1, 3, 6] 
b = [3, 1, 6]
sorted(a) == sorted(b)
# True

Here you will find extensive discussion on this topic.

edited Nov 01 '18 at 17:04

answered Nov 01 '18 at 16:51

Sheldore

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Note that `sorted` has an average time complexity of *O(n log n)*. – blhsing Nov 01 '18 at 16:52
@blhsing: Hmm, right. May be the OP has small lists/vectors where it won't matter that much. But yes, for much larger lists, it might make a difference – Sheldore Nov 01 '18 at 16:53
@blhsing: What is the time complexity of `set`? – Sheldore Nov 01 '18 at 16:57

score 0 · Answer 3 · answered Nov 01 '18 at 16:57

0

Try This:

 set(a) == set(b)

Because set automatically sort.

answered Nov 01 '18 at 16:57

Rohit-Pandey

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Your approach will compare `[1, 1, 3, 6]` and `[3, 1, 6]` as equal. – timgeb Nov 01 '18 at 16:57
Right `set` contain only unique @timgeb. – Rohit-Pandey Nov 01 '18 at 16:59

compare two vector Python

3 Answers3