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/**
* `levenshtein-rs` - levenshtein
*
* MIT licensed.
*
* Copyright (c) 2016 Titus Wormer <tituswormer@gmail.com>
*/
#[must_use]
pub fn levenshtein(a: &str, b: &str) -> usize {
let mut result = 0;
/* Shortcut optimizations / degenerate cases. */
if a == b {
return result;
}
let length_a = a.chars().count();
let length_b = b.chars().count();
if length_a == 0 {
return length_b;
}
if length_b == 0 {
return length_a;
}
/* Initialize the vector.
*
* This is why it’s fast, normally a matrix is used,
* here we use a single vector. */
let mut cache: Vec<usize> = (1..).take(length_a).collect();
let mut distance_a;
let mut distance_b;
/* Loop. */
for (index_b, code_b) in b.chars().enumerate() {
result = index_b;
distance_a = index_b;
for (index_a, code_a) in a.chars().enumerate() {
distance_b = if code_a == code_b {
distance_a
} else {
distance_a + 1
};
distance_a = cache[index_a];
result = if distance_a > result {
if distance_b > result {
result + 1
} else {
distance_b
}
} else if distance_b > distance_a {
distance_a + 1
} else {
distance_b
};
cache[index_a] = result;
}
}
result
}
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