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@codemonkey-uk
Last active Jan 2, 2016
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Provide self contained function template implementing the Breadth First Search algorithm.Does not depend on STL, or any other library code. Circa 2003.
// -------------------------------------------------------------------------
// bfs.h
// Version: 1.1
// Date: 2003/04/14
// Purpose: Provide template for Breadth First Search algorithm
// Note: Self contained, does not depend on STL, or any other library code
// (c) T.Frogley 2003-2015
// -------------------------------------------------------------------------
#ifndef TFROGLEY_BFS_H_2003
#define TFROGLEY_BFS_H_2003
namespace bfs {
// helper type(s), do not overload, specialise etc
namespace helper{
template<typename T>
struct node_link {
node_link( const T& node, node_link<T>* parent=0 )
: m_node(node)
, m_parent(parent)
, m_next(0)
, m_last(0)
{ }
T m_node;
node_link<T>* const m_parent;
node_link<T>* m_next;
node_link<T>* m_last;
};
}
// function template, bfs
// Does a Breadth First Search from 'a' until it finds 'b'
// If a path/route is found, returns true and
// Outputs into 'results' full path, including end nodes
// Else, returns false.
// NodeType requirements:
// * NodeType must appear to be a Container of NodeTypes, that is:
// -> Must have a "iterator" type, and have begin() and end()
// -> Assignable (Copy Constructible)
// * Comparison operators: == and !=
template<typename NodeType, typename OutputIterator>
bool bfs(const NodeType a, const NodeType b, OutputIterator results)
{
bool found_route = false;
typedef bfs::helper::node_link<NodeType> node;
typedef typename NodeType::iterator NodeItr;
node * head = new node(a);
node * tail = head;
node * current = head;
while(current && current->m_node != b){
//add child nodes to graph
const NodeItr end = current->m_node.end();
for(NodeItr i = current->m_node.begin();i!=end;++i){
//check for circular paths
node * search_back = tail;
do{
if (search_back->m_node == *i){
//already visited this node
break;
}
//search_back = search_back->m_parent;
search_back = search_back->m_last;
}while(search_back);
if (!search_back){
tail->m_next = new node(*i,current);
tail->m_next->m_last = tail;
tail = tail->m_next;
}
}
//move to next node
current = current->m_next;
}
//found a route!
if (current){
found_route = true;
//work back up route
do{
//results.push_front( current->m_node );
*results++ = current->m_node;
current = current->m_parent;
}while(current);
}
//clean up memory
do{
current = head->m_next;
delete head;
head = current;
}while(head);
return found_route;
}
}
#endif
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