Returns True if the two strings only differ by one character

python

Solution

Interesting question. A natural approach would be to use a full-fledged Levenshtein distance (AKA "edit distance") and ensure it equals 1. However, for the special case of `1`, you can do better.

If the two strings are the same length, you clearly need to check that they differ in just one spot...:

if len(string1) == len(string2):
    count_diffs = 0
    for a, b in zip(string1, string2):
        if a!=b:
            if count_diffs: return False
            count_diffs += 1
    return True

If the length difference is above 1, then the result is clearly `False`.

The interesting case comes when the difference is exactly one -- in which case you must check if the longer string can be made into the shorter one by dropping exactly one character.

if abs(len(string1) - len(string2)) > 1: return False
if len(string1) < len(string2):
    string1, string2 = string2, string1

Here I'm swapping the strings, if needed, to ensure `string1` is longer by exactly one character.

Now, we want to iterate independently on each string:

it1 = iter(string1)
it2 = iter(string2)
count_diffs = 0
c1 = next(it1, None)
c2 = next(it2, None)
while True:
    if c1 != c2:
        if count_diffs: return False
        count_diffs = 1
        c1 = next(it1)
    else:
        try:
            c1 = next(it1)
            c2 = next(it2)
        except StopIteration: return True

I'll leave it up to you how to put together these snippets to make the overall function work as intended -- so you can show at least some understanding of Python, as you're being asked to display!-)

Problem

Write a function nearlyEqual to test whether two strings are nearly equal. Two strings string1 and string2 are nearly equal when string1 can be generated by a single mutation on string2. The fundtion should return a boolean (True or False). ``` """Returns True if the two strings only differ by one character. >>> nearlyEqual('python', 'perl') False >>> nearlyEqual('perl', 'pearl') True >>> nearlyEqual('python', 'jython') True >>> nearlyEqual('man', 'woman') False """ def nearlyEqual(string1, string2): string1 = input('First Word') string2 = input('Second Word') if string1 == string2: print (True) else: print (False) return nearlyEqual(string1,string2) print (nearlyEqual(string1,string2)) string1 = () string2 = () print, nearlyEqual(string1, string2) ```

Original source