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Permutations (view source)

Revision as of 01:47, 19 February 2018

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→‎Iterative
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=={{header|Rust}}==
===Iterative===
UsingUses the QuickPermHeap's algorithm. This solution assumes you want seperate copies of each permutation. An in-place version is possible, but is incompatible with the <code>Iterator</code> trait.
<lang rust>structpub QuickPerm<Tfn permutations(size: usize) -> Permutations {
QuickPermPermutations { idxs: (0..elems.len()+1size).collect(), elemsswaps: elemsvec![0; size], idxi: 10 }▼
idxs: Vec<usize>,▼
elems: Vec<T>,
idx: usize,
}
 
pub struct Permutations {
impl<T: Clone> QuickPerm<T> {
fn new(elemsidxs: Vec<Tusize>) -> Self {,
▲ idxsswaps: Vec<usize>,
▲ QuickPerm { idxs: (0..elems.len()+1).collect(), elems: elems, idx: 1 }
}i: usize,
}
 
impl<T: Clone> Iterator for QuickPerm<T>Permutations {
type Item = Vec<Tusize>;
 
fn next(&mut self) -> Option<Self::Item> {
if self.idxi ==> self.elems.len()0 { return None; }
loop {
 
if self.idxs[i >= self.idx]swaps.len() -={ 1return None; }
let other = if self.idx % 2 == 1 {if self.idxsswaps[self.idxi] }< elseself.i { 0break; };
self.elems.swap(swaps[self.idx,i] = other)0;
self.idxi += 1;
while self.idxs[self.idx] == 0 {}
self.idxs[.swap(self.idx]i, =(self.i & 1) * self.idxswaps[self.i]);
self.idxswaps[self.i] += 1;
}
Some(self.elems.clone())i = 1;
Some(self.idxs.clone())
}
}
 
fn main() {
let perms = permutations(3).collect::<Vec<_>>();
for perm in QuickPerm::new(vec![1,2,3]) {
printlnassert_eq!("{:?}"perms, perm);vec![
vec![0, 1, 2],
}▼
vec![1, 0, 2],
vec![2, 0, 1],
vec![0, 2, 1],
vec![1, 2, 0],
vec![2, 1, 0],
▲ }]);
}</lang>
 
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