Class: Pathfinding::AStarFinder

Inherits:
Object
  • Object
show all
Defined in:
lib/pathfinding/a_star_finder.rb

Overview

An A* Pathfinder to build roads/paths between two coordinates containing different path costs, the heuristic behaviour that can be altered via configuration

Instance Method Summary collapse

Instance Method Details

#find_path(start_node, end_node, grid) ⇒ Object 



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# File 'lib/pathfinding/a_star_finder.rb', line 12

def find_path(start_node, end_node, grid)
  came_from = {}
  g_score = { start_node => 0 }
  f_score = { start_node => manhattan_distance(start_node, end_node) }

  open_set = Pathfinding::PriorityQueue.new
  open_set.push(start_node, f_score[start_node])

  closed_set = Set.new
  until open_set.empty?
    current = open_set.pop

    # Early exit if the current node is in the closed set
    next if closed_set.include?(current)

    # Mark the current node as visited
    closed_set.add(current)

    return reconstruct_path(came_from, current) if current == end_node

    grid.neighbors(current).each do |neighbor|
      tentative_g_score = g_score[current] + 1

      next if closed_set.include?(neighbor) || (g_score[neighbor] && tentative_g_score >= g_score[neighbor])

      came_from[neighbor] = current
      g_score[neighbor] = tentative_g_score
      f_score[neighbor] = g_score[neighbor] + heuristic_cost_estimate(neighbor, end_node)

      open_set.push(neighbor, f_score[neighbor])
    end
  end

  # No path found
  []
end