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Remove LCS

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Andras Schmelczer 2024-11-23 11:44:05 +00:00
parent 7f6973389f
commit 08910f1454
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2 changed files with 0 additions and 166 deletions
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165
backend/reconcile/src/diffs/lcs.rs
View file

@ -1,165 +0,0 @@
//! LCS diff algorithm.
//!
//! * time: `O((NM)D log (M)D)`
//! * space `O(MN)`
use std::collections::BTreeMap;
use std::ops::{Index, Range};
use crate::tokenizer::token::Token;
use super::raw_operation::RawOperation;
use super::utils::{common_prefix_len, common_suffix_len};
/// LCS diff algorithm.
/// Copied from https://github.com/mitsuhiko/similar/blob/7e15c44de11a1cd61e1149189929e189ef977fd8/src/algorithms/lcs.rs
pub fn diff(old: &[Token], new: &[Token]) -> Vec<RawOperation> {
let common_prefix_len = common_prefix_len(old, 0..old.len(), new, 0..new.len());
let common_suffix_len = common_suffix_len(
old,
common_prefix_len..old.len(),
new,
common_prefix_len..new.len(),
);
let maybe_table = make_table(
old,
common_prefix_len..(old.len() - common_suffix_len),
new,
common_prefix_len..(new.len() - common_suffix_len),
);
let mut old_idx = 0;
let mut new_idx = 0;
let new_len = new.len() - common_prefix_len - common_suffix_len;
let old_len = old.len() - common_prefix_len - common_suffix_len;
let mut result: Vec<RawOperation> = Vec::new();
if common_prefix_len > 0 {
result.push(RawOperation::Equal(old[0..common_prefix_len].to_vec()));
}
if let Some(table) = maybe_table {
while new_idx < new_len && old_idx < old_len {
let old_orig_idx = common_prefix_len + old_idx;
let new_orig_idx = common_prefix_len + new_idx;
if new[new_orig_idx] == old[old_orig_idx] {
result.push(RawOperation::Equal(vec![old[old_orig_idx].clone()]));
old_idx += 1;
new_idx += 1;
} else if table.get(&(new_idx, old_idx + 1)).unwrap_or(&0)
>= table.get(&(new_idx + 1, old_idx)).unwrap_or(&0)
{
result.push(RawOperation::Delete(vec![old[old_orig_idx].clone()]));
old_idx += 1;
} else {
result.push(RawOperation::Insert(vec![new[new_orig_idx].clone()]));
new_idx += 1;
}
}
} else {
let old_orig_idx = common_prefix_len + old_idx;
let new_orig_idx = common_prefix_len + new_idx;
result.push(RawOperation::Delete(
old[old_orig_idx..old_orig_idx + old_len].to_vec(),
));
result.push(RawOperation::Insert(
new[new_orig_idx..new_orig_idx + new_len].to_vec(),
));
}
if old_idx < old_len {
result.push(RawOperation::Delete(
old[common_prefix_len + old_idx..common_prefix_len + old_len].to_vec(),
));
old_idx += old_len - old_idx;
}
if new_idx < new_len {
result.push(RawOperation::Insert(
new[common_prefix_len + new_idx..common_prefix_len + new_len].to_vec(),
));
}
if common_suffix_len > 0 {
result.push(RawOperation::Equal(
old[old_len + common_prefix_len..old_len + common_prefix_len + common_suffix_len]
.to_vec(),
));
}
result
}
fn make_table<Old, New>(
old: &Old,
old_range: Range<usize>,
new: &New,
new_range: Range<usize>,
) -> Option<BTreeMap<(usize, usize), u32>>
where
Old: Index<usize> + ?Sized,
New: Index<usize> + ?Sized,
New::Output: PartialEq<Old::Output>,
{
let old_len = old_range.len();
let new_len = new_range.len();
let mut table = BTreeMap::new();
for i in (0..new_len).rev() {
for j in (0..old_len).rev() {
let val = if new[i] == old[j] {
table.get(&(i + 1, j + 1)).unwrap_or(&0) + 1
} else {
*table
.get(&(i + 1, j))
.unwrap_or(&0)
.max(table.get(&(i, j + 1)).unwrap_or(&0))
};
if val > 0 {
table.insert((i, j), val);
}
}
}
Some(table)
}
#[cfg(test)]
mod tests {
use super::*;
use pretty_assertions::assert_eq;
use std::collections::BTreeMap;
#[test]
fn test_table() {
let table = make_table(&vec![2, 3], 0..2, &vec![0, 1, 2], 0..3).unwrap();
let expected = {
let mut m = BTreeMap::new();
m.insert((1, 0), 1);
m.insert((0, 0), 1);
m.insert((2, 0), 1);
m
};
assert_eq!(table, expected);
}
#[test]
fn test_empty_examples() {
assert_eq!(diff(&[], &[]), vec![]);
assert_eq!(
diff(&[Token::new("a".to_string(), "a".to_string())], &[]),
vec![RawOperation::Delete(vec![Token::new(
"a".to_string(),
"a".to_string()
)])]
);
assert_eq!(
diff(&[], &[Token::new("a".to_string(), "a".to_string())]),
vec![RawOperation::Insert(vec![Token::new(
"a".to_string(),
"a".to_string()
)])]
);
}
}

1
backend/reconcile/src/diffs/mod.rs
View file

@ -1,4 +1,3 @@
pub mod lcs;
pub mod myers;
pub mod raw_operation;
mod utils;