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A_star.py
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A_star.py
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#A*
import heapq
def a_star(start, goal, graph, heuristic):
frontier = []
heapq.heappush(frontier, (0, start))
came_from = {}
cost_so_far = {}
came_from[start] = None
cost_so_far[start] = 0
while frontier:
current = heapq.heappop(frontier)[1]
if current == goal:
break
for next in graph[current]:
new_cost = cost_so_far[current] + graph[current][next]
if next not in cost_so_far or new_cost < cost_so_far[next]:
cost_so_far[next] = new_cost
priority = new_cost + heuristic(goal, next)
heapq.heappush(frontier, (priority, next))
came_from[next] = current
path = []
current = goal
while current != start:
path.append(current)
current = came_from[current]
path.append(start)
path.reverse()
return path
# Example Usage
graph = {
'A': {'B': 5, 'C': 10, 'D': 8},
'B': {'E': 6},
'C': {'E': 3, 'F': 2},
'D': {'F': 7},
'E': {'G': 6},
'F': {'G': 3},
'G': {}
}
heuristic = lambda a, b: abs(ord(a) - ord(b))
start = str(input("Enter Start state: ")) #A
goal = str(input("Enter Goal state: ")) #G
path = a_star(start, goal, graph, heuristic)
print(path) # Output: ['A', 'C', 'F', 'G']