mentat/petgraph/visit/fn.depth_first_search.html
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<h1 class='fqn'><span class='in-band'>Function <a href='../index.html'>petgraph</a>::<wbr><a href='index.html'>visit</a>::<wbr><a class="fn" href=''>depth_first_search</a></span><span class='out-of-band'><span id='render-detail'>
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[<span class='inner'>&#x2212;</span>]
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</span><a class='srclink' href='../../src/petgraph/visit/dfsvisit.rs.html#148-162' title='goto source code'>[src]</a></span></h1>
<pre class='rust fn'>pub fn depth_first_search&lt;G, I, F, C&gt;(graph: G, starts: I, visitor: F) -&gt; C <span class="where fmt-newline">where<br>&nbsp;&nbsp;&nbsp;&nbsp;G: <a class="trait" href="../../petgraph/visit/trait.IntoNeighbors.html" title="trait petgraph::visit::IntoNeighbors">IntoNeighbors</a> + <a class="trait" href="../../petgraph/visit/trait.Visitable.html" title="trait petgraph::visit::Visitable">Visitable</a>,<br>&nbsp;&nbsp;&nbsp;&nbsp;I: <a class="trait" href="https://doc.rust-lang.org/nightly/core/iter/traits/trait.IntoIterator.html" title="trait core::iter::traits::IntoIterator">IntoIterator</a>&lt;Item = G::<a class="type" href="../../petgraph/visit/trait.GraphBase.html#associatedtype.NodeId" title="type petgraph::visit::GraphBase::NodeId">NodeId</a>&gt;,<br>&nbsp;&nbsp;&nbsp;&nbsp;F: <a class="trait" href="https://doc.rust-lang.org/nightly/core/ops/function/trait.FnMut.html" title="trait core::ops::function::FnMut">FnMut</a>(<a class="enum" href="../../petgraph/visit/enum.DfsEvent.html" title="enum petgraph::visit::DfsEvent">DfsEvent</a>&lt;G::<a class="type" href="../../petgraph/visit/trait.GraphBase.html#associatedtype.NodeId" title="type petgraph::visit::GraphBase::NodeId">NodeId</a>&gt;) -&gt; C,<br>&nbsp;&nbsp;&nbsp;&nbsp;C: <a class="trait" href="../../petgraph/visit/trait.ControlFlow.html" title="trait petgraph::visit::ControlFlow">ControlFlow</a>,&nbsp;</span></pre><div class='docblock'><p>A recursive depth first search.</p>
<p>Starting points are the nodes in the iterator <code>starts</code> (specify just one
start vertex <em>x</em> by using <code>Some(x)</code>).</p>
<p>The traversal emits discovery and finish events for each reachable vertex,
and edge classification of each reachable edge. <code>visitor</code> is called for each
event, see <a href="enum.DfsEvent.html"><code>DfsEvent</code></a> for possible values.</p>
<p>If the return value of the visitor is simply <code>()</code>, the visit runs until it
is finished. If the return value is a <code>Control&lt;B&gt;</code>, it can be used to
break the visit early, and the last control value is returned by the
function.</p>
<h1 id="example" class="section-header"><a href="#example">Example</a></h1>
<p>Find a path from vertex 0 to 5, and exit the visit as soon as we reach
the goal vertex.</p>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">petgraph</span>::<span class="ident">prelude</span>::<span class="kw-2">*</span>;
<span class="kw">use</span> <span class="ident">petgraph</span>::<span class="ident">graph</span>::<span class="ident">node_index</span> <span class="kw">as</span> <span class="ident">n</span>;
<span class="kw">use</span> <span class="ident">petgraph</span>::<span class="ident">visit</span>::<span class="ident">depth_first_search</span>;
<span class="kw">use</span> <span class="ident">petgraph</span>::<span class="ident">visit</span>::{<span class="ident">DfsEvent</span>, <span class="ident">Control</span>};
<span class="kw">let</span> <span class="ident">gr</span>: <span class="ident">Graph</span><span class="op">&lt;</span>(), ()<span class="op">&gt;</span> <span class="op">=</span> <span class="ident">Graph</span>::<span class="ident">from_edges</span>(<span class="kw-2">&amp;</span>[
(<span class="number">0</span>, <span class="number">1</span>), (<span class="number">0</span>, <span class="number">2</span>), (<span class="number">0</span>, <span class="number">3</span>),
(<span class="number">1</span>, <span class="number">3</span>),
(<span class="number">2</span>, <span class="number">3</span>), (<span class="number">2</span>, <span class="number">4</span>),
(<span class="number">4</span>, <span class="number">0</span>), (<span class="number">4</span>, <span class="number">5</span>),
]);
<span class="comment">// record each predecessor, mapping node → node</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">predecessor</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="ident">NodeIndex</span>::<span class="ident">end</span>(); <span class="ident">gr</span>.<span class="ident">node_count</span>()];
<span class="kw">let</span> <span class="ident">start</span> <span class="op">=</span> <span class="ident">n</span>(<span class="number">0</span>);
<span class="kw">let</span> <span class="ident">goal</span> <span class="op">=</span> <span class="ident">n</span>(<span class="number">5</span>);
<span class="ident">depth_first_search</span>(<span class="kw-2">&amp;</span><span class="ident">gr</span>, <span class="prelude-val">Some</span>(<span class="ident">start</span>), <span class="op">|</span><span class="ident">event</span><span class="op">|</span> {
<span class="kw">if</span> <span class="kw">let</span> <span class="ident">DfsEvent</span>::<span class="ident">TreeEdge</span>(<span class="ident">u</span>, <span class="ident">v</span>) <span class="op">=</span> <span class="ident">event</span> {
<span class="ident">predecessor</span>[<span class="ident">v</span>.<span class="ident">index</span>()] <span class="op">=</span> <span class="ident">u</span>;
<span class="kw">if</span> <span class="ident">v</span> <span class="op">==</span> <span class="ident">goal</span> {
<span class="kw">return</span> <span class="ident">Control</span>::<span class="ident">Break</span>(<span class="ident">v</span>);
}
}
<span class="ident">Control</span>::<span class="ident">Continue</span>
});
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">next</span> <span class="op">=</span> <span class="ident">goal</span>;
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">path</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="ident">next</span>];
<span class="kw">while</span> <span class="ident">next</span> <span class="op">!=</span> <span class="ident">start</span> {
<span class="kw">let</span> <span class="ident">pred</span> <span class="op">=</span> <span class="ident">predecessor</span>[<span class="ident">next</span>.<span class="ident">index</span>()];
<span class="ident">path</span>.<span class="ident">push</span>(<span class="ident">pred</span>);
<span class="ident">next</span> <span class="op">=</span> <span class="ident">pred</span>;
}
<span class="ident">path</span>.<span class="ident">reverse</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&amp;</span><span class="ident">path</span>, <span class="kw-2">&amp;</span>[<span class="ident">n</span>(<span class="number">0</span>), <span class="ident">n</span>(<span class="number">2</span>), <span class="ident">n</span>(<span class="number">4</span>), <span class="ident">n</span>(<span class="number">5</span>)]);</pre>
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