count duplicates between two arrays or strings

Question

a = 'rrgb'
b = 'rggb'

I have these two strings. I am trying to count the correct amount of duplicates. The result should be three, b has 3 of the correct letters. But everything I find online returns 4 since technically they're the same letters. What is the best way to do this?

Pretty unclear what you mean with "duplicates" and "correct" and how you're counting. — Stefan Pochmann, Feb 24 '18 at 22:45
I agree, the question is very ambiguously worded. If `a = "xyz"` and `b = "zyx"`, then should your result be `1` or `3`? If `a = "XYZ"` and `b = "xyz"`, then should your result be `0` or `3`? If `a = "x y z"` and `b = "x y z"`, then should your result be `3` or `5`? If `a = "xxy"` and `b = "xxy"`, then should your result be `2` or `3`? You need to be more specific than *"count the correct amount of duplicates ... of the correct letters"*, because the answers below have taken different interpretations of this vague sentence and will yield different results. — Tom Lord, Feb 25 '18 at 01:02
When you post a question it's a good idea to check back from time-to-time in case--as here--readers ask for clarification. — Cary Swoveland, Feb 25 '18 at 02:13

score 4 · Accepted Answer · answered Feb 24 '18 at 23:42

4

a = 'rrgb'
b = 'rggb'

p a.chars.zip(b.chars).count{|c1, c2| c1 == c2} # => 3

answered Feb 24 '18 at 23:42

steenslag

79,051
16
138
171

1

Seeing the OP's answer, you seem to have interpreted the question correctly. – Cary Swoveland Feb 25 '18 at 03:23
Upvoted for `zip` preventing `O(N²)`, but `chars` would discard combined diacritics (and screw up the result in general on e.g. `'bär'` vs `'bar'`. – Aleksei Matiushkin Feb 25 '18 at 05:30
@mudasobwa I guess that to prevent that, the strings should be `unicode_normalize`d beforehand. – steenslag Feb 25 '18 at 12:14

count duplicates between two arrays or strings

1 Answers1