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Working LCS/SMS :)

This commit is contained in:
william 2023-06-18 21:52:49 -04:00
parent 7cc7d3bb76
commit 93d460ae5d
2 changed files with 158 additions and 106 deletions
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205
src/diff.rs
View File

@ -3,28 +3,71 @@
use std::collections::HashMap;
#[derive(Debug)]
pub struct DiffItem {
start_a: usize,
start_b: usize,
deleted_a: usize,
inserted_b: usize,
}
struct DiffData {
length: usize,
codes: Vec<usize>,
modified: Vec<bool>,
}
pub fn diff(a: &str, b: &str) {
struct SmsData {
x: usize,
y: usize,
}
struct DiffVec {
data: Vec<usize>,
}
impl DiffVec {
fn get(&self, index: usize) -> usize {
self.data[index]
}
fn get_i32(&self, index: i32) -> usize {
if index < 0 {
panic!("Got index < 0");
}
self.get(index as usize)
}
fn set(&mut self, index: usize, val: usize) {
self.data[index] = val;
}
fn set_i32(&mut self, index: i32, val: usize) {
if index < 0 {
panic!("Got index < 0");
}
self.set(index as usize, val);
}
}
pub fn diff(a: &str, b: &str) -> Vec<DiffItem> {
let mut existing_hashes: HashMap<&str, usize> = HashMap::new();
let mut data_a = diff_data(a, &mut existing_hashes);
let mut data_b = diff_data(b, &mut existing_hashes);
let max = data_a.length + data_b.length;
let mut down_vector = vec![0usize; 2 * max + 2];
let mut up_vector = vec![0usize; 2 * max + 2];
let mut down_vector = DiffVec { data: vec![0usize; 2 * max + 2] };
let mut up_vector = DiffVec { data: vec![0usize; 2 * max + 2] };
let upper_a = data_a.length;
let upper_b = data_b.length;
lcs(&mut data_a, 0, upper_a, &mut data_b, 0, upper_b, &mut down_vector, &mut up_vector);
optimize(&data_a);
optimize(&data_b);
optimize(&mut data_a);
optimize(&mut data_b);
create_diffs(&data_a, &data_b)
}
@ -62,7 +105,7 @@ fn diff_codes<'a>(text: &'a str, existing_hashes: &mut HashMap<&'a str, usize>)
}
// Longest Common-Subsequence
fn lcs(data_a: &mut DiffData, mut lower_a: usize, mut upper_a: usize, data_b: &mut DiffData, mut lower_b: usize, mut upper_b: usize, down_vector: &mut Vec<usize>, up_vector: &mut Vec<usize>) {
fn lcs(data_a: &mut DiffData, mut lower_a: usize, mut upper_a: usize, data_b: &mut DiffData, mut lower_b: usize, mut upper_b: usize, down_vector: &mut DiffVec, up_vector: &mut DiffVec) {
while lower_a < upper_a && lower_b < upper_b && data_a.codes[lower_a] == data_b.codes[lower_b] {
lower_a += 1;
lower_b += 1;
@ -76,37 +119,40 @@ fn lcs(data_a: &mut DiffData, mut lower_a: usize, mut upper_a: usize, data_b: &m
if lower_a == upper_a {
// Inserted lines
while lower_b < upper_b {
lower_b += 1;
data_b.modified[lower_b] = true;
lower_b += 1;
}
} else if lower_b == upper_b {
// Deleted lines
while lower_a < upper_a {
lower_a += 1;
data_a.modified[lower_a] = true;
lower_a += 1;
}
} else {
// Find the middle snake and length of an optimal path for A and B
let sms = sms(&data_a, &data_b, down_vector, up_vector);
let sms = sms(&data_a, lower_a, upper_a, &data_b, lower_b, upper_b, down_vector, up_vector);
// The path is from lower_x to (x, y) and (x, y) to upper_x
lcs(data_a, lower_a, sms.0, data_b, lower_b, sms.1, down_vector, up_vector);
lcs(data_a, sms.1, upper_a, data_b, sms.1, upper_b, down_vector, up_vector);
lcs(data_a, lower_a, sms.x, data_b, lower_b, sms.y, down_vector, up_vector);
lcs(data_a, sms.x, upper_a, data_b, sms.y, upper_b, down_vector, up_vector);
}
}
// https://stackoverflow.com/questions/54035728/how-to-add-a-negative-i32-number-to-an-usize-variable
fn add_i32(index: usize, offset: i32) -> usize {
if offset.is_negative() {
index - offset.wrapping_abs() as u32 as usize
} else {
index + offset as usize
}
}
// Shortest Middle Snake
fn sms(data_a: &DiffData, data_b: &DiffData, down_vector: &mut Vec<usize>, up_vector: &mut Vec<usize>) -> (usize, usize) {
let lower_a = 0usize;
let upper_a = data_a.length;
let lower_b = 0usize;
let upper_b = data_b.length;
fn sms(data_a: &DiffData, lower_a: usize, upper_a: usize, data_b: &DiffData, lower_b: usize, upper_b: usize, down_vector: &mut DiffVec, up_vector: &mut DiffVec) -> SmsData {
let max = upper_a as i32 + upper_b as i32 + 1;
let mut ret = (0usize, 0usize);
let max = data_a.length - data_b.length - 1;
let down_k = lower_a - lower_b;
let up_k = upper_a - upper_b;
let down_k = lower_a as i32 - lower_b as i32;
let up_k = upper_a as i32 - upper_b as i32;
let delta = (upper_a - lower_a) - (upper_b - lower_b);
let odd_delta = (delta & 1) != 0;
@ -114,28 +160,28 @@ fn sms(data_a: &DiffData, data_b: &DiffData, down_vector: &mut Vec<usize>, up_ve
let down_offset = max - down_k;
let up_offset = max - up_k;
let max_d = ((upper_a - lower_a + upper_b - lower_b) / 2) + 1;
let max_d = ((upper_a - lower_a + upper_b - lower_b) / 2) as i32 + 1;
down_vector[down_offset + down_k + 1] = lower_a;
up_vector[up_offset + up_k - 1] = upper_a;
down_vector.set_i32(down_offset + down_k + 1, lower_a);
up_vector.set_i32(up_offset + up_k - 1, upper_a);
for d in 0..=max_d {
// Extend the forward path
for k in ((down_k - d)..=(down_k + d)).step_by(2) {
let mut x = 0;
let mut y = 0;
let mut x;
let mut y;
if k == down_k - d {
// Down
x = down_vector[down_offset + k + 1];
x = down_vector.get_i32(down_offset + k + 1);
} else {
// Right
x = down_vector[down_offset + k - 1];
if k < down_k + d && down_vector[down_offset + k + 1] >= 1 {
x = down_vector.get_i32(down_offset + k - 1) + 1;
if k < down_k + d && down_vector.get_i32(down_offset + k + 1) >= x {
// Down
x = down_vector[down_offset + k + 1];
x = down_vector.get_i32(down_offset + k + 1);
}
}
y = x - k;
y = add_i32(x, -k);
// Find the end of the furthest reaching forward D-path in diagonal k.
while x < upper_a && y < upper_b && data_a.codes[x] == data_b.codes[y] {
@ -143,46 +189,46 @@ fn sms(data_a: &DiffData, data_b: &DiffData, down_vector: &mut Vec<usize>, up_ve
y += 1;
}
down_vector[down_offset + k] = x;
down_vector.set_i32(down_offset + k, x);
// Overlap ?
if odd_delta && up_k - d < k && k < up_k + d && up_vector[up_offset + k] <= down_vector[down_offset + k] {
ret.0 = down_vector[down_offset + k];
ret.1 = down_vector[down_offset + k] - k;
return ret;
if odd_delta && up_k - d < k && k < up_k + d && up_vector.get_i32(up_offset + k) <= down_vector.get_i32(down_offset + k) {
let x = down_vector.get_i32(down_offset + k);
let y = add_i32(down_vector.get_i32(down_offset + k), -k);
return SmsData { x, y };
}
}
// Extend the reverse path
for k in ((up_k - d)..=(up_k + d)).step_by(2) {
let mut x = 0;
let mut y = 0;
let mut x;
let mut y;
if k == up_k + d {
// Up
x = up_vector[up_offset + k - 1];
x = up_vector.get_i32(up_offset + k - 1);
} else {
// Left
x = up_vector[up_offset + k + 1] - 1;
if k > up_k - d && up_vector[up_offset + k - 1] < x {
x = up_vector.get_i32(up_offset + k + 1) - 1;
if k > up_k - d && up_vector.get_i32(up_offset + k - 1) < x {
// Up
x = up_vector[up_offset + k - 1];
x = up_vector.get_i32(up_offset + k - 1);
}
}
y = x - k;
y = add_i32(x, -k);
while x > lower_a && y > lower_b && data_a.codes[x - 1] == data_b.codes[y - 1] {
x -= 1;
y -= 1;
}
up_vector[up_offset + k] = x;
up_vector.set_i32(up_offset + k, x);
// Overlap ?
if !odd_delta && down_k - d <= k && k <= down_k + d && up_vector[up_offset + k] <= down_vector[down_offset + k] {
ret.0 = down_vector[down_offset + k];
ret.1 = down_vector[down_offset + k] - k;
return ret;
if !odd_delta && down_k - d <= k && k <= down_k + d && up_vector.get_i32(up_offset + k) <= down_vector.get_i32(down_offset + k) {
let x = down_vector.get_i32(down_offset + k);
let y = add_i32(down_vector.get_i32(down_offset + k), -k);
return SmsData { x, y };
}
}
}
@ -190,6 +236,65 @@ fn sms(data_a: &DiffData, data_b: &DiffData, down_vector: &mut Vec<usize>, up_ve
panic!("This should not be possible :(");
}
fn optimize(data: &DiffData) {}
fn optimize(data: &mut DiffData) {
let mut start_pos = 0usize;
let mut end_pos;
fn create_diffs(data_a: &DiffData, data_b: &DiffData) {}
while start_pos < data.length {
while start_pos < data.length && !data.modified[start_pos] {
start_pos += 1;
}
end_pos = start_pos;
while end_pos < data.length && data.modified[end_pos] {
end_pos += 1;
}
if end_pos < data.length && data.codes[start_pos] == data.codes[end_pos] {
data.modified[start_pos] = false;
data.modified[end_pos] = true;
} else {
start_pos = end_pos;
}
}
}
fn create_diffs(data_a: &DiffData, data_b: &DiffData) -> Vec<DiffItem> {
let mut result = Vec::new();
let mut start_a;
let mut start_b;
let mut line_a = 0usize;
let mut line_b = 0usize;
while line_a < data_a.length || line_b < data_b.length {
if line_a < data_a.length && !data_a.modified[line_a] &&
line_b < data_b.length && !data_b.modified[line_b] {
// Equal line
line_a += 1;
line_b += 1;
} else {
start_a = line_a;
start_b = line_b;
while line_a < data_a.length && (line_b >= data_b.length || data_a.modified[line_a]) {
line_a += 1;
}
while line_b < data_b.length && (line_a >= data_a.length || data_b.modified[line_b]) {
line_b += 1;
}
if start_a < line_a || start_b < line_b {
let item = DiffItem {
start_a,
start_b,
deleted_a: line_a - start_a,
inserted_b: line_b - start_b,
};
result.push(item);
}
}
}
result
}

59
src/main.rs
View File

@ -6,61 +6,8 @@ mod diff;
fn main() {
let a = "abcabba\nlkajsdfasdf\nasdfasdfasdf\nlasjkdf";
let b = "abcabba\ncbabasdfasdf\nlasjkdf";
let b = "abcabba\ncbabasdfasdf\nlasjkdf\nope";
diff(a, b);
// lcs(a, b);
let result = diff(a, b);
dbg!(result);
}
// fn lcs(a: &str, b: &str) {
// let n = a.len() as i32;
// let m = b.len() as i32;
// let max = n + m;
// let mut endpoints = vec![0i32; max as usize * 2];
//
// for script_length in 0..max {
// let mut k = -script_length;
// while k <= script_length * 2 {
// let index = (k + max) as usize + 1;
// let previous_endpoint = endpoints[index - 1];
// let next_endpoint = endpoints[index + 1];
//
// let mut x = if k == -script_length || k != script_length && previous_endpoint < next_endpoint {
// next_endpoint
// } else {
// previous_endpoint + 1
// };
//
// let mut y = if k < x {
// x - k
// } else {
// 0
// };
//
// // Increase x and y as long as we are in a common sequence between a and b
// while x < n && y < m {
// let ac = a.chars().nth(x as usize).unwrap();
// let bc = b.chars().nth(y as usize).unwrap();
//
// if ac != bc {
// break;
// }
//
// x += 1;
// y += 1;
// }
//
// endpoints[index] = x;
//
// // We have traveled through both strings, the length of the shortest edit script (SES) has been found.
// if x >= n && y >= m {
// println!("Length of a SES is D ({d})");
// return;
// }
//
// k += 2;
// }
// }
//
// println!("Length of a SES is greater than MAX ({max})");
// }