How to compare strings for 3/4 matches - ruby

Question

Need to compare numbers in an array to 'winning' number. But I have to see if 3 out of 4 match. eg "1234" is my number and winning=["4356","8312","4820","7623"] . In this case "8312" should alert a win because they have 1 2&3 in common. I have to define the numbers in a unit test, then write a function in a separate file then pass that function back into the unit test. Any help would be greatly appreciated. I already wrote a function and test comparing for an exact match and dont have any idea on what next step to take.
function_file
def match(my_num,arr)
matches = []
arr.each_with_index do |v,i|
if my_num == v
matches << my_num
end
end
matches
end
test_file
require "minitest/autorun"
require_relative "close_but_no_func.rb"
class TestWinningNumbers < Minitest::Test
def test_1_equals_1
assert_equal(10-5, 3+2)
end
def test_winning_num
my_num = "1134"
arr=["6028","2088","3058","3476","8740","1134"]
assert_equal(["1134"], match(my_num, arr))
end
end

Answer 1

So let us divide this problem into two seperate problems.
You want a function that counts the number of matching characters.
Then you want to collect these strings together, if they have enough matching characters.
You could for example write a function that checks how many characters of the both strings match.
def count_matching_chars(str1,str2)
# counts how many characters of str1 appear in str2
matching_chars_count = 0
str1.each_char do |char|
matching_chars_count += 1 if str2.include?(char)
end
matching_chars_count
end
puts count_matching_chars("1234", "1134") => 3
puts count_matching_chars("1111", "1134") => 4
puts count_matching_chars("1234", "1111") => 1
This one here ignores the positioning, it just checks, how many of the characters of str1 match one character of str2.
Now you can easily collect these numbers in an array.
def matches(my_num, arr)
result = []
arr.each do |num|
result << arr if count_matching_chars(my_num,num) >= 3
end
result
end
You can write both functions in a more compact way, by using enumerator functions like count and select:
def count_matching_chars(str1,str2)
str1.each_char.count do |char|
str2.include?(char)
end
end
def matches(my_num, arr)
arr.select do |num|
return true if count_matching_chars(num,my_num) >= 3
end
end
Or you then combine everything into one function
def matches(my_num, arr)
arr.select do |num|
true if my_num.each_char.count { |char| num.include?(char)} >= 3
end
end
Now if you just want to check, if it is a winning number. You just return true as soon as you find a match:
def winning_number?(my_num, arr)
arr.select do |num|
return true if my_num.each_char.count { |char| num.include?(char)} >= 3
end
end