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// ==========================================================================
// SeqAn - The Library for Sequence Analysis
// ==========================================================================
// Copyright (c) 2006-2026, Knut Reinert, FU Berlin
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// * Neither the name of Knut Reinert or the FU Berlin nor the names of
// its contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL KNUT REINERT OR THE FU BERLIN BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
// DAMAGE.
//
// ==========================================================================
// Author: Tobias Raussch <rausch@embl.de>
// Author: Ryan Wick <rrwick@gmail.com>
// ==========================================================================
// Implementation of Depth-First-Search algorithm.
// ==========================================================================
#ifndef INCLUDE_SEQAN_GRAPH_ALGORITHMS_DEPTH_FIRST_SEARCH_H_
#define INCLUDE_SEQAN_GRAPH_ALGORITHMS_DEPTH_FIRST_SEARCH_H_
namespace seqan2 {
// ============================================================================
// Forwards
// ============================================================================
// ============================================================================
// Tags, Classes, Enums
// ============================================================================
// ============================================================================
// Metafunctions
// ============================================================================
// ============================================================================
// Functions
// ============================================================================
// ----------------------------------------------------------------------------
// Function depthFirstSearch()
// ----------------------------------------------------------------------------
/*!
* @fn depthFirstSearch
* @headerfile <seqan/graph_algorithms.h>
* @brief Implements a depth-first search on a graph.
*
* @signature void depthFirstSearch(predecessor, discovery, finish, g);
*
* @param[out] predecessor A property map.Predecessor subgraph produced by the depth-first search.
* @param[out] discovery A property map.The discovery time of a vertex v.
* @param[out] finish A property map.The time when v's adjacency list has been fully explored.
* @param[in] g A graph. Types: Undirected Graph, Directed Graph
*
* In contrast to a breadth-first search the depth-first search is repeated from multiple sources if the graph is not
* connected. Hence, depth-first search produces a depth-first forest. To ensure each vertex ends up in exactly one
* tree we need not just a distance but a discovery and finishing time.
*
* @section Example
*
* @include demos/dox/graph_algorithms/depth_first_search.cpp
*
* @include demos/dox/graph_algorithms/depth_first_search.cpp.stdout
*
* @see breadthFirstSearch
*/
template <typename TSpec, typename TPredecessorMap, typename TDiscoveryTimeMap, typename TFinishingTimeMap>
void depthFirstSearch(TPredecessorMap & predecessor,
TDiscoveryTimeMap & disc,
TFinishingTimeMap & finish,
Graph<TSpec> const & g)
{
typedef Graph<TSpec> TGraph;
typedef typename Size<TGraph>::Type TSize;
typedef typename Iterator<TGraph, VertexIterator>::Type TVertexIterator;
typedef typename VertexDescriptor<TGraph>::Type TVertexDescriptor;
typedef typename Value<TPredecessorMap>::Type TPredVal;
typedef typename Iterator<Graph<TSpec>, AdjacencyIterator>::Type TAdjacencyIterator;
enum class _DfsTask : uint8_t
{
EXPLORE,
FINISH
};
// Initialization - set each vertex as unvisited and with no predecessor.
resizeVertexMap(predecessor, g);
resizeVertexMap(disc, g);
resizeVertexMap(finish, g);
TPredVal nil = getNil<TVertexDescriptor>();
String<bool> tokenMap;
resizeVertexMap(tokenMap, g);
TVertexIterator it(g);
for(;!atEnd(it);goNext(it))
{
assignProperty(tokenMap, getValue(it), false);
assignProperty(predecessor, getValue(it), nil);
}
TSize time = 0;
// We do the DFS non-recursively using a stack. The stack holds two possible tasks:
// EXPLORE, which means we must follow that vertex's edges
// FINISH, which means the vertex just needs a finish time
std::vector<std::pair<TVertexDescriptor, _DfsTask> > vStack;
// The graph may not be connected, so start at every vertex.
goBegin(it);
for(; !atEnd(it); goNext(it))
{
// If the vertex has already been visited, skip it.
TVertexDescriptor v = getValue(it);
if (getProperty(tokenMap, v))
{
continue;
}
vStack.clear();
vStack.emplace_back(v, _DfsTask::EXPLORE);
while (!vStack.empty())
{
// Get the vertex and task from the top of the stack.
auto stackItem = vStack.back();
vStack.pop_back();
TVertexDescriptor v = stackItem.first;
if (stackItem.second == _DfsTask::FINISH)
{
assignProperty(finish, v, ++time);
}
else if (!getProperty(tokenMap, v)) // If the task is EXPLORE and the vertex is not visited...
{
assignProperty(tokenMap, v, true); // label as visited
assignProperty(disc, v, ++time); // set discovery time
vStack.emplace_back(v, _DfsTask::FINISH); // add a task to the stack so the vertex will get a finish time
// Add EXPLORE tasks to the stack for each unvisited adjacent vertex. They are added in reverse order
// so the first adjacent vertex will be the first to come off the stack. This is to mimic the behaviour
// of the original recursive implementation of this function.
TAdjacencyIterator itad(g, v);
goEnd(itad);
while (!atBegin(itad))
{
goPrevious(itad);
TVertexDescriptor nextV = getValue(itad);
if (!getProperty(tokenMap, nextV))
{
vStack.emplace_back(nextV, _DfsTask::EXPLORE);
assignProperty(predecessor, nextV, v);
}
}
}
}
}
}
} // namespace seqan2
#endif // #ifndef INCLUDE_SEQAN_GRAPH_ALGORITHMS_DEPTH_FIRST_SEARCH_H_
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