README.md

Edit Distance

Write a function that returns whether two words are exactly "one edit" away using the following signature: bool OneEditApart(string s1, string s2); An edit is:

• Inserting one character anywhere in the word (including at the beginning and end)
• Removing one character
• Replacing one character

Examples:

OneEditApart("cat", "dog") = false
OneEditApart("cat", "cats") = true
OneEditApart("cat", "cut") = true
OneEditApart("cat", "cast") = true
OneEditApart("cat", "at") = true
OneEditApart("cat", "act") = false

one_edit_apart.py

def one_edit_apart(s_one, s_two):
    s1, s2 = sorted([s_one, s_two], key=len, reverse=True)
    
    if len(s1) == len(s2):
        for index, (l1, l2) in enumerate(zip(s1, s2)):
            if l1 != l2:
                return string_without(s1, index) == string_without(s2, index)
        return True

    if len(s1) == len(s2) + 1:
        for index, (l1, l2) in enumerate(zip(s1, s2)):
            if l1 != l2:
                return string_without(s1, index) == s2
        return True

    return False

def string_without(s, index):
    return s[:index] + s[index+1:]

import unittest
class TestSpiralMethods(unittest.TestCase):
    def test_no_where_near(self):
        self.assertFalse(one_edit_apart('cat', 'dog'))

    def test_too_many_diffs(self):
        self.assertFalse(one_edit_apart('cat', 'act'))

    def test_same(self):
        self.assertTrue(one_edit_apart('cat', 'cat'))

    def test_one_letter_difference(self):
        self.assertTrue(one_edit_apart('cat', 'car'))

    def test_add_a_letter_at_the_end(self):
        self.assertTrue(one_edit_apart('cat', 'cats'))

    def test_add_a_letter_at_the_start(self):
        self.assertTrue(one_edit_apart('rat', 'drat'))

    def test_add_a_letter_in_the_middle(self):
        self.assertTrue(one_edit_apart('cat', 'cart'))

    def test_add_a_letter_in_the_middle_of_a_diff_string(self):
        self.assertFalse(one_edit_apart('dog', 'cart'))
    
    def test_add_two_letters(self):
        self.assertFalse(one_edit_apart('cat', 'catss'))


unittest.main(exit=False)