Unicode-aware Levenshtein distance by Rust

levenshtein_distance.rs

fn main() {
    fn f(a:&str, b:&str) {
        println!("{}:{} => {}", a, b, levenshtein_distance(a, b));
    }
    f("こんにちは", "こんばんは");
    f("hello", "ell0");
    f("hello", "hello");
    f("こんにちは", "hello");
    f("ABC", "AＢC");
    f("\u{1F369}", "\u{1F36A}");
}

fn levenshtein_distance(a:&str, b:&str) -> usize {
    let ac: Vec<char> = a.chars().collect();
    let bc: Vec<char> = b.chars().collect();
    let alen = ac.len() + 1;
    let blen = bc.len() + 1;
    let mut mat = vec![vec![0; blen]; alen];
    for i in (0..blen) { mat[0][i] = i; }
    for i in (1..alen) {
        mat[i][0] = i;
        for j in (1..blen) {
            let m = [mat[i - 1][j] + 1,
                     mat[i][j - 1] + 1,
                     mat[i - 1][j - 1] + if ac[i - 1] == bc[j - 1] { 0 } else { 1 }];
            mat[i][j] = *m.iter().min().unwrap();
        }
    }
    return mat[alen - 1][blen - 1];
}

output

こんにちは:こんばんは => 2
hello:ell0 => 2
hello:hello => 0
こんにちは:hello => 5
ABC:AＢC => 1
🍩:🍪 => 1