Created
May 22, 2021 09:57
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Works for r = 3, almost works for other r
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use std::{fmt::Debug, ops::Range}; | |
fn main() { | |
let mut v = vec![1, 2, 3, 4, 5, 6]; | |
let r = 3; | |
for x in CombiIterator::new(&mut v, r) { | |
println!("{:?}", x); | |
} | |
} | |
struct CombiIterator<'a, T> { | |
slice: &'a mut [T], | |
range: Range<usize>, | |
r: usize, | |
step: usize, | |
end: usize, | |
} | |
impl<'a, T> CombiIterator<'a, T> { | |
fn new(slice: &'a mut [T], r: usize) -> Self { | |
let n = slice.len(); | |
Self { | |
slice, | |
range: r - 1..n, | |
r, | |
step: 0, | |
end: n, | |
} | |
} | |
} | |
impl<'a, T: Clone + Debug> Iterator for CombiIterator<'a, T> { | |
type Item = Vec<T>; | |
fn next(&mut self) -> Option<Self::Item> { | |
if self.end < self.r { | |
return None; | |
} | |
let output = self.slice[..self.r].to_vec(); | |
self.slice[self.range.clone()].rotate_left(1); | |
self.step += 1; | |
if self.step == self.range.len() { | |
if self.range.len() == 1 { | |
self.slice[1..self.end].rotate_left(self.r - 1); | |
self.slice[..].rotate_left(1); | |
self.end -= 1; | |
self.range.end = self.end; | |
} else { | |
self.slice[(self.range.start - 1)..self.end].rotate_left(1); | |
self.range.end -= 1; | |
} | |
self.step = 0; | |
} | |
Some(output) | |
} | |
} |
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