/** Calculate shortest path lengths in @a g from the nearest node to @a point.
* @param[in,out] g Input graph
* @param[in] point Point to find the nearest node to.
* @post Graph has modified node values indicating the minimum path length
* to the nearest node to @a point
* @post Graph nodes that are unreachable to the nearest node to @a point have
* the value() -1.
* @return The maximum path length found.
*
* Finds the nearest node to @a point and treats that as the root node for a
* breadth first search.
* This sets node's value() to the length of the shortest path to
* the root node. The root's value() is 0. Nodes unreachable from
* the root have value() -1.
*/
int shortest_path_lengths(Graph<int>& g, const Point& point) {
// TYPE DEFINIATIONS
typedef Graph<int> GraphType;
typedef GraphType::node_type Node;
typedef std::pair <Node,int> Pair;
// apply find closest node
auto root = std::min_element(g.node_begin(), g.node_end(), MyComparator(point));
// initiate queue for BFS
std::queue<Pair> bfs;
// initialize default distance from point and push node and distance value in queue
int distance = 1;
bfs.push(Pair(*root, distance));
// initialize pair variables for the queue
Pair node_distance;
Pair next;
// Dequeue and add adjacent nodes not yet searched to the queue while updating distance
while(!bfs.empty()){
node_distance = bfs.front();
for (auto it = node_distance.first.edge_begin(); it != node_distance.first.edge_end(); ++it){
if ((*it).node1() != node_distance.first)
next.first = (*it).node1();
else
next.first = (*it).node2();
if (next.first.value() == 0){
distance = node_distance.second;
next.first.value() = distance;
next.second = ++distance;
bfs.push(next);
}
}
bfs.pop();
}
// change the value of nodes not found to -1 and update root node value to 0
for (auto it = g.node_begin(); it != g.node_end(); ++it){
if ((*it).value() == 0)
(*it).value() = -1;
}
(*root).value() = 0;
return distance;
}
/** Calculate shortest path lengths in @a g from the nearest node to @a point.
* @param[in,out] g Input graph
* @param[in] point Point to find the nearest node to.
* @post Graph has modified node values indicating the minimum path length
* to the nearest node to @a point
* @post Graph nodes that are unreachable to the nearest node to @a point have
* the value() -1.
* @return The maximum path length found.
*
* Finds the nearest node to @a point and treats that as the root node for a
* breadth first search.
* This sets node's value() to the length of the shortest path to
* the root node. The root's value() is 0. Nodes unreachable from
* the root have value() -1.
*/
int shortest_path_lengths(Graph<int, int>& g, const Point& point) {
MyComparator mc = MyComparator(point);
// Find the closest node to the given Point as root.
Graph<int, int>::node_iterator nifirst = g.node_begin();
Graph<int, int>::node_iterator nilast = g.node_end();
Graph<int, int>::node_iterator niroot = std::min_element(nifirst, nilast, mc);
Graph<int, int>::node_type root = *niroot;
// Set all the nodes' default values to -1 and the root's value to 0.
for(; nifirst != nilast; ++nifirst){
(*nifirst).value() = -1;
}
root.value() = 0;
// Set the current longest distance from root.
int max = 0;
/** The queue is to store the nodes needed to be evaluated.
* For each node n in the queue, we iterate the adjent nodes and set their values,
* push them into the queue and then pop n. In this process, update max.
*/
std::queue<Graph<int, int>::node_type> waiting;
waiting.push(root);
while(!waiting.empty()){
Graph<int, int>::node_type r = waiting.front();
int cur = r.value();
Graph<int, int>::incident_iterator rbegin = r.edge_begin();
Graph<int, int>::incident_iterator rend = r.edge_end();
for(; rbegin != rend; ++rbegin){
if((*rbegin).node2().value() == -1){
(*rbegin).node2().value() = cur + 1;
if((*rbegin).node2().value() > max) max = (*rbegin).node2().value();
waiting.push((*rbegin).node2());
}
if((*rbegin).node2().value() > cur + 1){
(*rbegin).node2().value() = cur + 1;
if((*rbegin).node2().value() > max) max = (*rbegin).node2().value();
}
}
waiting.pop();
}
return max;
}
