added 8 puzzle problem using A star algorithm

Author: Prathamesh-1011

other/8PuzzleProblem_Astar.py

@@ -0,0 +1,77 @@
+import copy
+import heapq
+
+class Puzzle:
+    
+    def __init__(self, initial_state):
+        self.goal_state = [[1, 2, 3], [4, 5, 6], [7, 8, 0]]
+        self.initial_state = initial_state
+        self.open_list = []
+        self.closed_list = []
+    
+    def get_heuristic(self, state):
+        heuristic = 0
+        for i in range(3):
+            for j in range(3):
+                if state[i][j] != 0:
+                    x_goal, y_goal = divmod(state[i][j] - 1, 3)
+                    heuristic += abs(i - x_goal) + abs(j - y_goal)
+        return heuristic
+    
+    def get_blank_position(self, state):
+        for i in range(3):
+            for j in range(3):
+                if state[i][j] == 0:
+                    return (i, j)
+    
+    def get_successors(self, state):
+        successors = []
+        i_blank, j_blank = self.get_blank_position(state)
+        for x, y in [(0, 1), (1, 0), (0, -1), (-1, 0)]:
+            if 0 <= i_blank + x < 3 and 0 <= j_blank + y < 3:
+                new_state = copy.deepcopy(state)
+                new_state[i_blank][j_blank], new_state[i_blank + x][j_blank + y] = new_state[i_blank + x][j_blank + y], new_state[i_blank][j_blank]
+                successors.append(new_state)
+        return successors
+    
+    def solve(self):
+        start_node = (self.get_heuristic(self.initial_state), self.initial_state, 0, None)
+        heapq.heappush(self.open_list, start_node)
+        
+        while self.open_list:
+            current_node = heapq.heappop(self.open_list)
+            current_cost = current_node[2]
+            current_state = current_node[1]
+            
+            if current_state == self.goal_state:
+                path = []
+                while current_node:
+                    path.append(current_node[1])
+                    current_node = current_node[3]
+                return reversed(path)
+            
+            self.closed_list.append(current_state)
+            successors = self.get_successors(current_state)
+            for successor in successors:
+                if successor not in self.closed_list:
+                    g_cost = current_cost + 1
+                    h_cost = self.get_heuristic(successor)
+                    f_cost = g_cost + h_cost
+                    new_node = (f_cost, successor, g_cost, current_node)
+                    heapq.heappush(self.open_list, new_node)
+        
+        return None
+
+# Run the Solver
+initial_state = [[1,2, 3], [4,5,6], [0,7,8]]
+solver = Puzzle(initial_state)
+solution = solver.solve()
+
+if solution:
+    for idx, state in enumerate(solution):
+        print(f"Move {idx + 1}:")
+        for row in state:
+            print(row)
+        print()
+else:
+    print("No solution found.")