def levenshtein_distance(s1: str, s2: str) -> int:
    if len(s1) > len(s2):
        s1, s2 = s2, s1

    distances = list(range(len(s1) + 1))
    for i2, c2 in enumerate(s2):
        distances_ = [i2 + 1]
        for i1, c1 in enumerate(s1):
            if c1 == c2:
                distances_.append(distances[i1])
            else:
                distances_.append(1 + min((distances[i1], distances[i1 + 1], distances_[-1])))
        distances = distances_
    return distances[-1]