AI Programs
IMPLEMENT A* SEARCH ALGORITHM.
class Node():
def __init__(self, parent=None, position=None):
self.parent = parent
self.position = position
self.g = 0
self.h = 0
self.f = 0
def __eq__(self, other):
return self.position == other.position
def astar(maze, start, end):
start_node = Node(None, start)
start_node.g = start_node.h = start_node.f = 0
end_node = Node(None, end)
end_node.g = end_node.h = end_node.f = 0
open_list = []
closed_list = []
open_list.append(start_node)
while len(open_list) > 0:
current_node = open_list[0]
current_index = 0
for index, item in enumerate(open_list):
if item.f < current_node.f:
current_node = item
current_index = index
open_list.pop(current_index)
closed_list.append(current_node)
if current_node == end_node:
path = []
current = current_node
while current is not None:
path.append(current.position)
current = current.parent
return path[::-1]
children = []
for new_position in [(0, -1), (0, 1), (-1, 0), (1, 0), (-1, -1), (-1, 1), (1, -1), (1, 1)]:
node_position = (current_node.position[0] + new_position[0], current_node.position[1] + new_position[1])
if node_position[0] > (len(maze) - 1) or node_position[0] < 0 or node_position[1] > (
len(maze[len(maze) - 1]) - 1) or node_position[1] < 0:
continue
if maze[node_position[0]][node_position[1]] != 0:
continue
new_node = Node(current_node, node_position)
children.append(new_node)
for child in children:
for closed_child in closed_list:
if child == closed_child:
continue
child.g = current_node.g + 1
child.h = ((child.position[0] - end_node.position[0]) ** 2) + (
(child.position[1] - end_node.position[1]) ** 2)
child.f = child.g + child.h
for open_node in open_list:
if child == open_node and child.g > open_node.g:
continue
open_list.append(child)
def main():
maze = [[0, 0, 0, 0, 1, 0],
[0, 0, 0, 0, 1, 0],
[0, 0, 0, 0, 1, 0],
[0, 0, 0, 0, 1, 0],
[0, 0, 0, 0, 1, 0],
[0, 0, 0, 0, 0, 0]]
graph = [[0, 1, 0, 0, 0, 0],
[1, 0, 1, 0, 1, 0],
[0, 1, 0, 0, 0, 1],
[0, 0, 0, 0, 1, 0],
[0, 1, 0, 1, 0, 0],
[0, 0, 1, 0, 0, 0]]
start = (0, 0)
end = (5, 5)
end1 = (5, 5)
path = astar(maze, start, end)
print("path",path)
path1 = astar(graph, start, end1)
print("path1",path1)
if __name__ == '__main__':
main()
Output of A Star Search Algorithm
path
[(0,0),(1,1),(2,2),(3,3),(4.3),(5,4),(5,5)]
Path1 [(0,0),(1,1),(2,2),(3,3),(4,4),(5,5)]
-----------------------------------------------------------------------------------------------------------------------------
IMPLEMENT AO* SEARCH ALGORITHM.
class Graph:
def __init__(self, graph, heuristicNodeList, startNode): #instantiate graph object with graph topology, heuristic values, start node
self.graph = graph
self.H=heuristicNodeList
self.start=startNode
self.parent={}
self.status={}
self.solutionGraph={}
def applyAOStar(self): # starts a recursive AO* algorithm
self.aoStar(self.start, False)
def getNeighbors(self, v): # gets the Neighbors of a given node
return self.graph.get(v,'')
def getStatus(self,v): # return the status of a given node
return self.status.get(v,0)
def setStatus(self,v, val): # set the status of a given node
self.status[v]=val
def getHeuristicNodeValue(self, n):
return self.H.get(n,0) # always return the heuristic value of a given node
def setHeuristicNodeValue(self, n, value):
self.H[n]=value # set the revised heuristic value of a given node
def printSolution(self):
print("FOR GRAPH SOLUTION, TRAVERSE THE GRAPH FROM THE START NODE:",self.start)
print("------------------------------------------------------------")
print(self.solutionGraph)
print("------------------------------------------------------------")
def computeMinimumCostChildNodes(self, v): # Computes the Minimum Cost of child nodes of a given node v
minimumCost=0
costToChildNodeListDict={}
costToChildNodeListDict[minimumCost]=[]
flag=True
for nodeInfoTupleList in self.getNeighbors(v): # iterate over all the set of child node/s
cost=0
nodeList=[]
for c, weight in nodeInfoTupleList:
cost=cost+self.getHeuristicNodeValue(c)+weight
nodeList.append(c)
if flag==True: # initialize Minimum Cost with the cost of first set of child node/s
minimumCost=cost
costToChildNodeListDict[minimumCost]=nodeList # set the Minimum Cost child node/s
flag=False
else: # checking the Minimum Cost nodes with the current Minimum Cost
if minimumCost>cost:
minimumCost=cost
costToChildNodeListDict[minimumCost]=nodeList # set the Minimum Cost child node/s
return minimumCost, costToChildNodeListDict[minimumCost] # return Minimum Cost and Minimum Cost child node/s
def aoStar(self, v, backTracking): # AO* algorithm for a start node and backTracking status flag
print("HEURISTIC VALUES :", self.H)
print("SOLUTION GRAPH :", self.solutionGraph)
print("PROCESSING NODE :", v)
print("-----------------------------------------------------------------------------------------")
if self.getStatus(v) >= 0: # if status node v >= 0, compute Minimum Cost nodes of v
minimumCost, childNodeList = self.computeMinimumCostChildNodes(v)
print(minimumCost, childNodeList)
self.setHeuristicNodeValue(v, minimumCost)
self.setStatus(v,len(childNodeList))
solved=True # check the Minimum Cost nodes of v are solved
for childNode in childNodeList:
self.parent[childNode]=v
if self.getStatus(childNode)!=-1:
solved=solved & False
if solved==True: # if the Minimum Cost nodes of v are solved, set the current node status as solved(-1)
self.setStatus(v,-1)
self.solutionGraph[v]=childNodeList # update the solution graph with the solved nodes which may be a part of solution
if v!=self.start: # check the current node is the start node for backtracking the current node value
self.aoStar(self.parent[v], True) # backtracking the current node value with backtracking status set to true
if backTracking==False: # check the current call is not for backtracking
for childNode in childNodeList: # for each Minimum Cost child node
self.setStatus(childNode,0) # set the status of child node to 0(needs exploration)
self.aoStar(childNode, False) # Minimum Cost child node is further explored with backtracking status as false
#for simplicity we ll consider heuristic distances given
print ("Graph - 1")
h1 = {'A': 1, 'B': 6, 'C': 2, 'D': 12, 'E': 2, 'F': 1, 'G': 5, 'H': 7, 'I': 7, 'J': 1}
graph1 = {
'A': [[('B', 1), ('C', 1)], [('D', 1)]],
'B': [[('G', 1)], [('H', 1)]],
'C': [[('J', 1)]],
'D': [[('E', 1), ('F', 1)]],
'G': [[('I', 1)]]
}
G1= Graph(graph1, h1, 'A')
G1.applyAOStar()
G1.printSolution()
Output of AO Star Search Algorithm
HEURISTIC VALUES :
{‘A’: 1, ‘B’: 6, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 5, ‘H’: 7, ‘I’: 7, ‘J’:
1}
SOLUTION GRAPH : {}
PROCESSING NODE : A
10 [‘B’, ‘C’]
HEURISTIC VALUES : {‘A’: 10, ‘B’: 6, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 5,
‘H’: 7, ‘I’: 7, ‘J’: 1}
SOLUTION GRAPH : {}
PROCESSING NODE : B
6 [‘G’]
HEURISTIC VALUES : {‘A’: 10, ‘B’: 6, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 5,
‘H’: 7, ‘I’: 7, ‘J’: 1}
SOLUTION GRAPH : {}
PROCESSING NODE : A
10 [‘B’, ‘C’]
HEURISTIC VALUES : {‘A’: 10, ‘B’: 6, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 5,
‘H’: 7, ‘I’: 7, ‘J’: 1}
SOLUTION GRAPH : {}
PROCESSING NODE : G
8 [‘I’]
HEURISTIC VALUES : {‘A’: 10, ‘B’: 6, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 8,
‘H’: 7, ‘I’: 7, ‘J’: 1}
SOLUTION GRAPH : {}
PROCESSING NODE : B
8 [‘H’]
HEURISTIC VALUES : {‘A’: 10, ‘B’: 8, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 8,
‘H’: 7, ‘I’: 7, ‘J’: 1}
SOLUTION GRAPH : {}
PROCESSING NODE : A
12 [‘B’, ‘C’]
HEURISTIC VALUES : {‘A’: 12, ‘B’: 8, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 8,
‘H’: 7, ‘I’: 7, ‘J’: 1}
SOLUTION GRAPH : {}
PROCESSING NODE : I
0 []
HEURISTIC VALUES : {‘A’: 12, ‘B’: 8, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 8,
‘H’: 7, ‘I’: 0, ‘J’: 1}
SOLUTION GRAPH : {‘I’: []}
PROCESSING NODE : G
1 [‘I’]
HEURISTIC VALUES : {‘A’: 12, ‘B’: 8, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 1,
‘H’: 7, ‘I’: 0, ‘J’: 1}
SOLUTION GRAPH : {‘I’: [], ‘G’: [‘I’]}
PROCESSING NODE : B
2 [‘G’]
HEURISTIC VALUES : {‘A’: 12, ‘B’: 2, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 1,
‘H’: 7, ‘I’: 0, ‘J’: 1}
SOLUTION GRAPH : {‘I’: [], ‘G’: [‘I’], ‘B’: [‘G’]}
PROCESSING NODE : A
6 [‘B’, ‘C’]
HEURISTIC VALUES : {‘A’: 6, ‘B’: 2, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 1,
‘H’: 7, ‘I’: 0, ‘J’: 1}
SOLUTION GRAPH : {‘I’: [], ‘G’: [‘I’], ‘B’: [‘G’]}
PROCESSING NODE : C
2 [‘J’]
HEURISTIC VALUES : {‘A’: 6, ‘B’: 2, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 1,
‘H’: 7, ‘I’: 0, ‘J’: 1}
SOLUTION GRAPH : {‘I’: [], ‘G’: [‘I’], ‘B’: [‘G’]}
PROCESSING NODE : A
6 [‘B’, ‘C’]
HEURISTIC VALUES : {‘A’: 6, ‘B’: 2, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 1,
‘H’: 7, ‘I’: 0, ‘J’: 1}
SOLUTION GRAPH : {‘I’: [], ‘G’: [‘I’], ‘B’: [‘G’]}
PROCESSING NODE : J
0 []
HEURISTIC VALUES : {‘A’: 6, ‘B’: 2, ‘C’: 2, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 1,
‘H’: 7, ‘I’: 0, ‘J’: 0}
SOLUTION GRAPH : {‘I’: [], ‘G’: [‘I’], ‘B’: [‘G’], ‘J’: []}
PROCESSING NODE : C
1 [‘J’]
HEURISTIC VALUES : {‘A’: 6, ‘B’: 2, ‘C’: 1, ‘D’: 12, ‘E’: 2, ‘F’: 1, ‘G’: 1,
‘H’: 7, ‘I’: 0, ‘J’: 0}
SOLUTION GRAPH : {‘I’: [], ‘G’: [‘I’], ‘B’: [‘G’], ‘J’: [], ‘C’: [‘J’]}
PROCESSING NODE : A
5 [‘B’, ‘C’]
FOR GRAPH SOLUTION,
TRAVERSE THE GRAPH FROM THE START NODE: A
{‘I’: [], ‘G’: [‘I’], ‘B’: [‘G’], ‘J’: [], ‘C’: [‘J’], ‘A’: [‘B’, ‘C’]}
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