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pub trait RLE {
type Data;
fn compress(&self) -> Vec<Run<Self::Data>>;
fn decompress(runs: Vec<Run<Self::Data>>) -> Vec<Self::Data>;
}
pub type Run<T> = (T, usize);
impl<T> RLE for Vec<T>
where
T: Clone + PartialEq,
{
type Data = T;
fn compress(&self) -> Vec<Run<Self::Data>> {
let mut runs = vec![];
if self.is_empty() {
return runs;
}
let mut idx = 0;
loop {
let first = &self[idx];
let run_length = self[idx..].iter().take_while(|&item| item == first).count();
runs.push((first.clone(), run_length));
idx += run_length;
if idx > self.len() - 1 {
break;
}
}
runs
}
fn decompress(runs: Vec<Run<Self::Data>>) -> Vec<Self::Data> {
runs.into_iter()
.map(|(item, size)| vec![item; size])
.flatten()
.collect()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn singleton() {
let data = "a".chars().collect::<Vec<_>>();
assert_eq!(Vec::<char>::compress(&data), vec![('a', 1),]);
}
#[test]
fn identity() {
let data = "aabbccddaabbaa".chars().collect::<Vec<_>>();
assert_eq!(Vec::<char>::decompress(data.compress()), data);
}
#[test]
fn repeated_singleton() {
let data = "aaaaaaaaaaaaa".chars().collect::<Vec<_>>();
assert_eq!(Vec::<char>::compress(&data), vec![('a', 13),]);
}
#[test]
fn empty_runs() {
let data = "".chars().collect::<Vec<_>>();
assert!(data.compress().is_empty());
}
#[test]
fn empty_decompress() {
assert!(Vec::<char>::decompress(vec![]).is_empty());
}
#[test]
fn check_runs1() {
let data = "aaaabbbbcccc".chars().collect::<Vec<_>>();
assert_eq!(data.compress(), vec![('a', 4), ('b', 4), ('c', 4)]);
}
#[test]
fn check_runs2() {
let data = "aabbccddaabbaa".chars().collect::<Vec<_>>();
assert_eq!(
data.compress(),
vec![
('a', 2),
('b', 2),
('c', 2),
('d', 2),
('a', 2),
('b', 2),
('a', 2)
]
);
}
}
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