Implementations of path finding algorithms.
From Wikipedia
function Dijkstra(Graph, source):
for each vertex v in Graph: // Initializations
dist[v] := infinity ; // Unknown distance function from source to v
previous[v] := undefined ; // Previous node in optimal path from source
dist[source] := 0 ; // Distance from source to source
Q := the set of all nodes in Graph ; // All nodes in the graph are unoptimized - thus are in Q
while Q is not empty: // The main loop
u := vertex in Q with smallest distance in dist[] ; // Start node in first case
if dist[u] = infinity:
break ; // all remaining vertices are
// inaccessible from source
remove u from Q ;
for each neighbor v of u: // where v has not yet been removed from Q.
alt := dist[u] + dist_between(u, v) ;
if alt < dist[v]: // Relax (u,v,a)
dist[v] := alt ;
previous[v] := u ;
decrease-key v in Q; // Reorder v in the Queue
return dist;
From Wikipedia
function A*(start, goal)
closedset := the empty set // The set of nodes already evaluated.
openset := {start} // The set of tentative nodes to be evaluated, initially containing the start node
came_from := the empty map // The map of navigated nodes.
g_score[start] := 0 // Cost from start along best known path.
// Estimated total cost from start to goal through y.
f_score[start] := g_score[start] + heuristic_cost_estimate(start, goal)
while openset is not empty
current := the node in openset having the lowest f_score[] value
if current = goal
return reconstruct_path(came_from, goal)
remove current from openset
add current to closedset
for each neighbor in neighbor_nodes(current)
if neighbor in closedset
continue
tentative_g_score := g_score[current] + dist_between(current,neighbor)
if neighbor not in openset or tentative_g_score < g_score[neighbor]
if neighbor not in openset
add neighbor to openset
came_from[neighbor] := current
g_score[neighbor] := tentative_g_score
f_score[neighbor] := g_score[neighbor] + heuristic_cost_estimate(neighbor, goal)
return failure
function reconstruct_path(came_from, current_node)
if came_from[current_node] is set
p := reconstruct_path(came_from, came_from[current_node])
return (p + current_node)
else
return current_node