| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/itertools-0.10.5/src/permutations.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>permutations.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../itertools/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../itertools/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="kw">use </span>alloc::vec::Vec; |
| <span class="kw">use </span>std::fmt; |
| <span class="kw">use </span>std::iter::once; |
| |
| <span class="kw">use </span><span class="kw">super</span>::lazy_buffer::LazyBuffer; |
| |
| <span class="doccomment">/// An iterator adaptor that iterates through all the `k`-permutations of the |
| /// elements from an iterator. |
| /// |
| /// See [`.permutations()`](crate::Itertools::permutations) for |
| /// more information. |
| </span><span class="attribute">#[must_use = <span class="string">"iterator adaptors are lazy and do nothing unless consumed"</span>] |
| </span><span class="kw">pub struct </span>Permutations<I: Iterator> { |
| vals: LazyBuffer<I>, |
| state: PermutationState, |
| } |
| |
| <span class="kw">impl</span><I> Clone <span class="kw">for </span>Permutations<I> |
| <span class="kw">where </span>I: Clone + Iterator, |
| I::Item: Clone, |
| { |
| <span class="macro">clone_fields!</span>(vals, state); |
| } |
| |
| <span class="attribute">#[derive(Clone, Debug)] |
| </span><span class="kw">enum </span>PermutationState { |
| StartUnknownLen { |
| k: usize, |
| }, |
| OngoingUnknownLen { |
| k: usize, |
| min_n: usize, |
| }, |
| Complete(CompleteState), |
| Empty, |
| } |
| |
| <span class="attribute">#[derive(Clone, Debug)] |
| </span><span class="kw">enum </span>CompleteState { |
| Start { |
| n: usize, |
| k: usize, |
| }, |
| Ongoing { |
| indices: Vec<usize>, |
| cycles: Vec<usize>, |
| } |
| } |
| |
| <span class="kw">enum </span>CompleteStateRemaining { |
| Known(usize), |
| Overflow, |
| } |
| |
| <span class="kw">impl</span><I> fmt::Debug <span class="kw">for </span>Permutations<I> |
| <span class="kw">where </span>I: Iterator + fmt::Debug, |
| I::Item: fmt::Debug, |
| { |
| <span class="macro">debug_fmt_fields!</span>(Permutations, vals, state); |
| } |
| |
| <span class="kw">pub fn </span>permutations<I: Iterator>(iter: I, k: usize) -> Permutations<I> { |
| <span class="kw">let </span><span class="kw-2">mut </span>vals = LazyBuffer::new(iter); |
| |
| <span class="kw">if </span>k == <span class="number">0 </span>{ |
| <span class="comment">// Special case, yields single empty vec; `n` is irrelevant |
| </span><span class="kw">let </span>state = PermutationState::Complete(CompleteState::Start { n: <span class="number">0</span>, k: <span class="number">0 </span>}); |
| |
| <span class="kw">return </span>Permutations { |
| vals, |
| state |
| }; |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>enough_vals = <span class="bool-val">true</span>; |
| |
| <span class="kw">while </span>vals.len() < k { |
| <span class="kw">if </span>!vals.get_next() { |
| enough_vals = <span class="bool-val">false</span>; |
| <span class="kw">break</span>; |
| } |
| } |
| |
| <span class="kw">let </span>state = <span class="kw">if </span>enough_vals { |
| PermutationState::StartUnknownLen { k } |
| } <span class="kw">else </span>{ |
| PermutationState::Empty |
| }; |
| |
| Permutations { |
| vals, |
| state |
| } |
| } |
| |
| <span class="kw">impl</span><I> Iterator <span class="kw">for </span>Permutations<I> |
| <span class="kw">where |
| </span>I: Iterator, |
| I::Item: Clone |
| { |
| <span class="kw">type </span>Item = Vec<I::Item>; |
| |
| <span class="kw">fn </span>next(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>::Item> { |
| <span class="self">self</span>.advance(); |
| |
| <span class="kw">let </span><span class="kw-2">&mut </span>Permutations { <span class="kw-2">ref </span>vals, <span class="kw-2">ref </span>state } = <span class="self">self</span>; |
| |
| <span class="kw">match </span><span class="kw-2">*</span>state { |
| PermutationState::StartUnknownLen { .. } => <span class="macro">panic!</span>(<span class="string">"unexpected iterator state"</span>), |
| PermutationState::OngoingUnknownLen { k, min_n } => { |
| <span class="kw">let </span>latest_idx = min_n - <span class="number">1</span>; |
| <span class="kw">let </span>indices = (<span class="number">0</span>..(k - <span class="number">1</span>)).chain(once(latest_idx)); |
| |
| <span class="prelude-val">Some</span>(indices.map(|i| vals[i].clone()).collect()) |
| } |
| PermutationState::Complete(CompleteState::Ongoing { <span class="kw-2">ref </span>indices, <span class="kw-2">ref </span>cycles }) => { |
| <span class="kw">let </span>k = cycles.len(); |
| <span class="prelude-val">Some</span>(indices[<span class="number">0</span>..k].iter().map(|<span class="kw-2">&</span>i| vals[i].clone()).collect()) |
| }, |
| PermutationState::Complete(CompleteState::Start { .. }) | PermutationState::Empty => <span class="prelude-val">None |
| </span>} |
| } |
| |
| <span class="kw">fn </span>count(<span class="self">self</span>) -> usize { |
| <span class="kw">fn </span>from_complete(complete_state: CompleteState) -> usize { |
| <span class="kw">match </span>complete_state.remaining() { |
| CompleteStateRemaining::Known(count) => count, |
| CompleteStateRemaining::Overflow => { |
| <span class="macro">panic!</span>(<span class="string">"Iterator count greater than usize::MAX"</span>); |
| } |
| } |
| } |
| |
| <span class="kw">let </span>Permutations { vals, state } = <span class="self">self</span>; |
| <span class="kw">match </span>state { |
| PermutationState::StartUnknownLen { k } => { |
| <span class="kw">let </span>n = vals.len() + vals.it.count(); |
| <span class="kw">let </span>complete_state = CompleteState::Start { n, k }; |
| |
| from_complete(complete_state) |
| } |
| PermutationState::OngoingUnknownLen { k, min_n } => { |
| <span class="kw">let </span>prev_iteration_count = min_n - k + <span class="number">1</span>; |
| <span class="kw">let </span>n = vals.len() + vals.it.count(); |
| <span class="kw">let </span>complete_state = CompleteState::Start { n, k }; |
| |
| from_complete(complete_state) - prev_iteration_count |
| }, |
| PermutationState::Complete(state) => from_complete(state), |
| PermutationState::Empty => <span class="number">0 |
| </span>} |
| } |
| |
| <span class="kw">fn </span>size_hint(<span class="kw-2">&</span><span class="self">self</span>) -> (usize, <span class="prelude-ty">Option</span><usize>) { |
| <span class="kw">match </span><span class="self">self</span>.state { |
| PermutationState::StartUnknownLen { .. } | |
| PermutationState::OngoingUnknownLen { .. } => (<span class="number">0</span>, <span class="prelude-val">None</span>), <span class="comment">// TODO can we improve this lower bound? |
| </span>PermutationState::Complete(<span class="kw-2">ref </span>state) => <span class="kw">match </span>state.remaining() { |
| CompleteStateRemaining::Known(count) => (count, <span class="prelude-val">Some</span>(count)), |
| CompleteStateRemaining::Overflow => (::std::usize::MAX, <span class="prelude-val">None</span>) |
| } |
| PermutationState::Empty => (<span class="number">0</span>, <span class="prelude-val">Some</span>(<span class="number">0</span>)) |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><I> Permutations<I> |
| <span class="kw">where |
| </span>I: Iterator, |
| I::Item: Clone |
| { |
| <span class="kw">fn </span>advance(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="kw">let </span><span class="kw-2">&mut </span>Permutations { <span class="kw-2">ref mut </span>vals, <span class="kw-2">ref mut </span>state } = <span class="self">self</span>; |
| |
| <span class="kw-2">*</span>state = <span class="kw">match </span><span class="kw-2">*</span>state { |
| PermutationState::StartUnknownLen { k } => { |
| PermutationState::OngoingUnknownLen { k, min_n: k } |
| } |
| PermutationState::OngoingUnknownLen { k, min_n } => { |
| <span class="kw">if </span>vals.get_next() { |
| PermutationState::OngoingUnknownLen { k, min_n: min_n + <span class="number">1 </span>} |
| } <span class="kw">else </span>{ |
| <span class="kw">let </span>n = min_n; |
| <span class="kw">let </span>prev_iteration_count = n - k + <span class="number">1</span>; |
| <span class="kw">let </span><span class="kw-2">mut </span>complete_state = CompleteState::Start { n, k }; |
| |
| <span class="comment">// Advance the complete-state iterator to the correct point |
| </span><span class="kw">for _ in </span><span class="number">0</span>..(prev_iteration_count + <span class="number">1</span>) { |
| complete_state.advance(); |
| } |
| |
| PermutationState::Complete(complete_state) |
| } |
| } |
| PermutationState::Complete(<span class="kw-2">ref mut </span>state) => { |
| state.advance(); |
| |
| <span class="kw">return</span>; |
| } |
| PermutationState::Empty => { <span class="kw">return</span>; } |
| }; |
| } |
| } |
| |
| <span class="kw">impl </span>CompleteState { |
| <span class="kw">fn </span>advance(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="kw-2">*</span><span class="self">self </span>= <span class="kw">match </span><span class="kw-2">*</span><span class="self">self </span>{ |
| CompleteState::Start { n, k } => { |
| <span class="kw">let </span>indices = (<span class="number">0</span>..n).collect(); |
| <span class="kw">let </span>cycles = ((n - k)..n).rev().collect(); |
| |
| CompleteState::Ongoing { |
| cycles, |
| indices |
| } |
| }, |
| CompleteState::Ongoing { <span class="kw-2">ref mut </span>indices, <span class="kw-2">ref mut </span>cycles } => { |
| <span class="kw">let </span>n = indices.len(); |
| <span class="kw">let </span>k = cycles.len(); |
| |
| <span class="kw">for </span>i <span class="kw">in </span>(<span class="number">0</span>..k).rev() { |
| <span class="kw">if </span>cycles[i] == <span class="number">0 </span>{ |
| cycles[i] = n - i - <span class="number">1</span>; |
| |
| <span class="kw">let </span>to_push = indices.remove(i); |
| indices.push(to_push); |
| } <span class="kw">else </span>{ |
| <span class="kw">let </span>swap_index = n - cycles[i]; |
| indices.swap(i, swap_index); |
| |
| cycles[i] -= <span class="number">1</span>; |
| <span class="kw">return</span>; |
| } |
| } |
| |
| CompleteState::Start { n, k } |
| } |
| } |
| } |
| |
| <span class="kw">fn </span>remaining(<span class="kw-2">&</span><span class="self">self</span>) -> CompleteStateRemaining { |
| <span class="kw">use </span><span class="self">self</span>::CompleteStateRemaining::{Known, Overflow}; |
| |
| <span class="kw">match </span><span class="kw-2">*</span><span class="self">self </span>{ |
| CompleteState::Start { n, k } => { |
| <span class="kw">if </span>n < k { |
| <span class="kw">return </span>Known(<span class="number">0</span>); |
| } |
| |
| <span class="kw">let </span>count: <span class="prelude-ty">Option</span><usize> = (n - k + <span class="number">1</span>..n + <span class="number">1</span>).fold(<span class="prelude-val">Some</span>(<span class="number">1</span>), |acc, i| { |
| acc.and_then(|acc| acc.checked_mul(i)) |
| }); |
| |
| <span class="kw">match </span>count { |
| <span class="prelude-val">Some</span>(count) => Known(count), |
| <span class="prelude-val">None </span>=> Overflow |
| } |
| } |
| CompleteState::Ongoing { <span class="kw-2">ref </span>indices, <span class="kw-2">ref </span>cycles } => { |
| <span class="kw">let </span><span class="kw-2">mut </span>count: usize = <span class="number">0</span>; |
| |
| <span class="kw">for </span>(i, <span class="kw-2">&</span>c) <span class="kw">in </span>cycles.iter().enumerate() { |
| <span class="kw">let </span>radix = indices.len() - i; |
| <span class="kw">let </span>next_count = count.checked_mul(radix) |
| .and_then(|count| count.checked_add(c)); |
| |
| count = <span class="kw">match </span>next_count { |
| <span class="prelude-val">Some</span>(count) => count, |
| <span class="prelude-val">None </span>=> { <span class="kw">return </span>Overflow; } |
| }; |
| } |
| |
| Known(count) |
| } |
| } |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="itertools" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
