Function distance 

pub fn distance(s1: &str, s2: &str) -> usize

Levenshtein edit distance between two strings.

The distance is the minimum number of single-character insertions, deletions, or substitutions required to transform s1 into s2.

Characters are counted as Unicode scalar values (chars), so an accented letter or an emoji counts as one character.

Examples

assert_eq!(lev::distance("kitten", "sitting"), 3);
assert_eq!(lev::distance("flaw", "lawn"), 2);
assert_eq!(lev::distance("résumé", "resume"), 2);
assert_eq!(lev::distance("日本語", "日本"), 1);