distance s t computes the Levenshtein (edit) distance between two UTF-8 encoded strings.

The Levenshtein distance is the minimum number of single-character edits (insertions, deletions, or substitutions) required to transform one string into another.

This implementation is Unicode-aware and correctly handles multibyte characters such as Japanese, Chinese, emoji, and accented letters.

Examples:

• distance "kitten" "sitting" returns 3
• distance "こんにちは" "こんばんは" returns 2
• distance "🍎" "🍏" returns 1

Malformed UTF-8 sequences are replaced with '?' during decoding.

• parameter s

  The first UTF-8 encoded string

• parameter t

  The second UTF-8 encoded string

• returns

  The edit distance between s and t