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use std::cmp;
use std::collections::HashMap;
use unicode_segmentation::UnicodeSegmentation;
fn range_vec(size: usize) -> Vec<usize> {
let mut vec = Vec::new();
let mut p: usize = 0;
vec.resize_with(size, || {
p += 1;
p - 1
});
return vec;
}
pub fn vec_levenshtein_distance<T: PartialEq>(v1: &Vec<T>, v2: &Vec<T>) -> usize {
let rows = v1.len() + 1;
let cols = v2.len() + 1;
if rows == 1 {
return cols - 1;
} else if cols == 1 {
return rows - 1;
}
let mut cur = range_vec(cols);
for r in 1..rows {
let prev = cur.to_vec();
cur = vec![0; cols];
cur[0] = r;
for c in 1..cols {
let del_or_ins = cmp::min(prev[c] + 1, cur[c - 1] + 1);
let edit = prev[c - 1] + (if v1[r - 1] == v2[c - 1] { 0 } else { 1 });
cur[c] = cmp::min(del_or_ins, edit);
}
}
return cur[cur.len() - 1];
}
pub fn vec_damerau_levenshtein_distance<T: Eq + std::hash::Hash>(
v1: &Vec<T>,
v2: &Vec<T>,
) -> usize {
let len1 = v1.len();
let len2 = v2.len();
let infinite = len1 + len2;
let mut item_position = HashMap::new();
let mut score = vec![vec![0; len2 + 2]; len1 + 2];
score[0][0] = infinite;
for i in 0..len1 + 1 {
score[i + 1][0] = infinite;
score[i + 1][1] = i;
}
for i in 0..len2 + 1 {
score[0][i + 1] = infinite;
score[1][i + 1] = i;
}
for i in 1..len1 + 1 {
let mut db = 0;
for j in 1..len2 + 1 {
let i1 = item_position.entry(&v2[j - 1]).or_insert(0);
let j1 = db;
let mut cost = 1;
if v1[i - 1] == v2[j - 1] {
cost = 0;
db = j;
}
score[i + 1][j + 1] = cmp::min(
cmp::min(score[i][j] + cost, score[i + 1][j] + 1),
cmp::min(
score[i][j + 1] + 1,
score[*i1][j1] + (i - *i1 - 1) + 1 + (j - j1 - 1),
),
)
}
item_position.insert(&v1[i - 1], i);
}
return score[len1 + 1][len2 + 1];
}
pub fn levenshtein_distance(s1: &str, s2: &str) -> usize {
if s1 == s2 {
return 0;
}
let us1 = UnicodeSegmentation::graphemes(s1, true).collect::<Vec<&str>>();
let us2 = UnicodeSegmentation::graphemes(s2, true).collect::<Vec<&str>>();
vec_levenshtein_distance(&us1, &us2)
}
pub fn damerau_levenshtein_distance(s1: &str, s2: &str) -> usize {
if s1 == s2 {
return 0;
}
let us1 = UnicodeSegmentation::graphemes(s1, true).collect::<Vec<&str>>();
let us2 = UnicodeSegmentation::graphemes(s2, true).collect::<Vec<&str>>();
vec_damerau_levenshtein_distance(&us1, &us2)
}
#[cfg(test)]
mod test {
use super::*;
use crate::testutils::testutils;
#[test]
fn test_levenshtein() {
testutils::test_distance_func("testdata/levenshtein.csv", levenshtein_distance);
}
#[test]
fn test_damerau_levenshtein() {
testutils::test_distance_func(
"testdata/damerau_levenshtein.csv",
damerau_levenshtein_distance,
);
}
}