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/// Iterator that yields consecutive runs of equal elements from a slice.
///
/// A run is a sequence of consecutive elements that are equal according to
/// [`PartialEq`]. The iterator yields references to subslices containing these runs.
///
/// # Type Parameters
///
/// * `'a` - Lifetime of the referenced slice
/// * `T` - Type of elements in the slice, must implement [`PartialEq`]
///
/// # Examples
///
/// ```
/// use toolbox_rs::run_iterator::RunIterator;
///
/// let array = [1, 1, 2, 2, 2, 3, 3, 1];
/// let runs: Vec<&[i32]> = RunIterator::new(&array).collect();
/// let expected: Vec<&[i32]> = vec![
/// &[1, 1], // First run of 1s
/// &[2, 2, 2], // Run of 2s
/// &[3, 3], // Run of 3s
/// &[1], // Single 1
/// ];
/// assert_eq!(runs, expected);
/// ```
pub struct RunIterator<'a, T> {
array: &'a [T],
pos: usize,
}
impl<'a, T: PartialEq> RunIterator<'a, T> {
/// Creates a new `RunIterator` from a slice.
///
/// # Arguments
///
/// * `array` - Slice to iterate over
///
/// # Examples
///
/// ```
/// use toolbox_rs::run_iterator::RunIterator;
///
/// let data = vec!["a", "a", "b", "c", "c"];
/// let iterator = RunIterator::new(&data);
/// ```
pub fn new(array: &'a [T]) -> Self {
RunIterator { array, pos: 0 }
}
}
impl<'a, T> RunIterator<'a, T> {
/// Creates a new `RunIterator` with a custom predicate for determining runs.
///
/// The predicate function determines if two consecutive elements belong to the same run.
/// Elements are grouped into runs as long as the predicate returns `true` for adjacent pairs.
///
/// # Arguments
///
/// * `array` - Slice to iterate over
/// * `pred` - Predicate function that takes two references and returns bool
///
/// # Examples
///
/// ```
/// use toolbox_rs::run_iterator::RunIterator;
///
/// // Group numbers by their difference being less than 2
/// let input = vec![1, 3, 4, 8, 9, 10, 15];
/// let result: Vec<&[i32]> = RunIterator::new_by(&input, |a, b| b - a <= 2).collect();
/// assert_eq!(result, vec![&input[0..3], &input[3..6], &input[6..]]);
///
/// // Group strings by their length
/// let strings = vec!["a", "b", "cd", "ef", "g"];
/// let runs: Vec<&[&str]> = RunIterator::new_by(&strings, |a, b| a.len() == b.len()).collect();
/// assert_eq!(runs, vec![&strings[0..2], &strings[2..4], &[strings[4]]]);
/// ```
pub fn new_by<F>(array: &'a [T], pred: F) -> RunIteratorBy<'a, T, F>
where
F: Fn(&T, &T) -> bool,
{
RunIteratorBy {
array,
pos: 0,
pred,
}
}
}
/// Iterator that yields runs of elements based on a custom predicate
pub struct RunIteratorBy<'a, T, F> {
array: &'a [T],
pos: usize,
pred: F,
}
impl<'a, T, F> Iterator for RunIteratorBy<'a, T, F>
where
F: Fn(&T, &T) -> bool,
{
type Item = &'a [T];
fn next(&mut self) -> Option<Self::Item> {
if self.pos >= self.array.len() {
return None;
}
let start = self.pos;
self.pos += 1;
while self.pos < self.array.len()
&& (self.pred)(&self.array[self.pos - 1], &self.array[self.pos])
{
self.pos += 1;
}
Some(&self.array[start..self.pos])
}
}
impl<'a, T: PartialEq> Iterator for RunIterator<'a, T> {
type Item = &'a [T];
/// Returns the next run of equal elements.
///
/// # Returns
///
/// * `Some(&[T])` - Reference to the next run of equal elements
/// * `None` - When iteration is complete
///
/// # Examples
///
/// ```
/// use toolbox_rs::run_iterator::RunIterator;
///
/// let data = vec![1, 1, 2, 2, 3];
/// let mut iter = RunIterator::new(&data);
///
/// assert_eq!(iter.next(), Some(&[1, 1][..]));
/// assert_eq!(iter.next(), Some(&[2, 2][..]));
/// assert_eq!(iter.next(), Some(&[3][..]));
/// assert_eq!(iter.next(), None);
/// ```
fn next(&mut self) -> Option<Self::Item> {
if self.pos >= self.array.len() {
return None;
}
let start = self.pos;
self.pos += 1;
self.pos += self.array[start + 1..]
.iter()
.position(|x| x != &self.array[start])
.unwrap_or(self.array.len() - start - 1);
Some(&self.array[start..self.pos])
}
}
#[cfg(test)]
mod tests {
use super::RunIterator;
#[test]
fn unsorted_runs_tests() {
let array = [1, 1, 2, 2, 2, 3, 3, 1];
let run_iter = RunIterator::new(&array);
let result: Vec<&[i32]> = run_iter.collect();
let expected: Vec<&[i32]> = vec![&[1; 2], &[2; 3], &[3; 2], &[1; 1]];
assert_eq!(expected, result);
}
#[test]
fn object_runs() {
#[derive(Debug)]
struct SimplePair {
key: i32,
_value: i32,
}
impl PartialEq for SimplePair {
fn eq(&self, other: &Self) -> bool {
self.key == other.key
}
}
let input = vec![
SimplePair { key: 1, _value: 2 },
SimplePair { key: 1, _value: 1 },
SimplePair { key: 21, _value: 1 },
SimplePair { key: 1, _value: 1 },
];
let run_iter = RunIterator::new(&input);
let result: Vec<&[SimplePair]> = run_iter.collect();
assert_eq!(3, result.len());
let expected = vec![&input[0..2], &input[2..3], &input[3..]];
assert_eq!(expected, result);
}
#[test]
fn test_custom_predicate() {
let input = vec![1, 3, 4, 8, 9, 10, 15];
let result: Vec<&[i32]> = RunIterator::new_by(&input, |a, b| b - a <= 2).collect();
// The expected runs are:
// [1, 3, 4], [8, 9, 10], [15]
assert_eq!(result, vec![&input[0..3], &input[3..6], &input[6..]]);
let inputs = vec![19, 21, 23, 20, 25, 18];
let result: Vec<&[i32]> = RunIterator::new_by(&inputs, |a, b| a % 2 == b % 2).collect();
// The expected runs are:
// [19, 21, 23], [20], [25], [18]
assert_eq!(
result,
vec![&inputs[0..3], &inputs[3..4], &inputs[4..5], &inputs[5..]]
);
}
}