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29 changes: 29 additions & 0 deletions hamming.rb
Original file line number Diff line number Diff line change
@@ -0,0 +1,29 @@
class Hamming

def self.compute(strand1, strand2)

raise ArgumentError if strand1.length != strand2.length

# base case
if strand1.empty? || strand2.empty?
return 0
end

# gets last element of array-type strand1 and strand2
nuc1 = strand1.split(//).pop
nuc2 = strand2.split(//).pop

adder = 0
if nuc1 != nuc2
adder = 1
end

# removes the final letter so string ending in next letter for comparison can be passed through recursion
strand1.chop!
strand2.chop!

return adder + self.compute(strand1, strand2)

end

end
14 changes: 0 additions & 14 deletions hamming_test.rb
Original file line number Diff line number Diff line change
Expand Up @@ -4,72 +4,58 @@

class HammingTest < Minitest::Test
def test_identical_strands
skip
assert_equal 0, Hamming.compute('A', 'A')
end

def test_long_identical_strands
skip
assert_equal 0, Hamming.compute('GGACTGA', 'GGACTGA')
end

def test_complete_distance_in_single_nucleotide_strands
skip
assert_equal 1, Hamming.compute('A', 'G')
end

def test_complete_distance_in_small_strands
skip
assert_equal 2, Hamming.compute('AG', 'CT')
end

def test_small_distance_in_small_strands
skip
assert_equal 1, Hamming.compute('AT', 'CT')
end

def test_small_distance
skip
assert_equal 1, Hamming.compute('GGACG', 'GGTCG')
end

def test_small_distance_in_long_strands
skip
assert_equal 2, Hamming.compute('ACCAGGG', 'ACTATGG')
end

def test_non_unique_character_in_first_strand
skip
assert_equal 1, Hamming.compute('AGA', 'AGG')
end

def test_non_unique_character_in_second_strand
skip
assert_equal 1, Hamming.compute('AGG', 'AGA')
end

def test_large_distance
skip
assert_equal 4, Hamming.compute('GATACA', 'GCATAA')
end

def test_large_distance_in_off_by_one_strand
skip
assert_equal 9, Hamming.compute('GGACGGATTCTG', 'AGGACGGATTCT')
end

def test_empty_strands
skip
assert_equal 0, Hamming.compute('', '')
end

def test_disallow_first_strand_longer
skip
assert_raises(ArgumentError) { Hamming.compute('AATG', 'AAA') }
end

def test_disallow_second_strand_longer
skip
assert_raises(ArgumentError) { Hamming.compute('ATA', 'AGTG') }
end
end