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8Puzzle_problem.py
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initial_state = [[1,2,3],[0,4,6],[7,5,8]]
final_state = [[1,2,3],[4,5,6],[7,8,0]]
val=0
#checking whether the inital abd final state are Same or not
def areSame(A,B):
for i in range(3):
for j in range(3):
if (A[i][j] != B[i][j]):
return False
return True
# counting the number of mismatches
def mismatches(A,B):
count_different = 0
for i in range(3):
for j in range(3):
if (A[i][j]!=B[i][j] and A[i][j]!=0):
count_different += 1
return count_different
# movements of the 0 box in all directions
# in this I have simply swappped the 0 box with the correct direction and then counted mismatches .
def moveDown(initial_state,row_index,column_index):
initial_state[row_index][column_index] , initial_state[row_index+1][column_index] = initial_state[row_index+1][column_index],initial_state[row_index][column_index]
different_elements = mismatches(initial_state,final_state)
initial_state[row_index+1][column_index],initial_state[row_index][column_index]=initial_state[row_index][column_index] , initial_state[row_index+1][column_index]
return different_elements
def moveUp(initial_state,row_index,column_index):
initial_state[row_index][column_index] , initial_state[row_index-1][column_index]= initial_state[row_index-1][column_index], initial_state[row_index][column_index]
different_elements=mismatches(initial_state,final_state)
initial_state[row_index-1][column_index], initial_state[row_index][column_index]=initial_state[row_index][column_index] , initial_state[row_index-1][column_index]
return different_elements
def moveLeft(initial_state,row_index,column_index):
initial_state[row_index][column_index], initial_state[row_index][column_index-1] = initial_state[row_index][column_index-1], initial_state[row_index][column_index]
different_elements=mismatches(initial_state,final_state)
initial_state[row_index][column_index-1], initial_state[row_index][column_index]=initial_state[row_index][column_index], initial_state[row_index][column_index-1]
return different_elements
def moveRight(initial_state,row_index,column_index):
initial_state[row_index][column_index] , initial_state[row_index][column_index+1] = initial_state[row_index][column_index+1],initial_state[row_index][column_index]
different_elements=mismatches(initial_state,final_state)
initial_state[row_index][column_index+1],initial_state[row_index][column_index]=initial_state[row_index][column_index] , initial_state[row_index][column_index+1]
return different_elements
#this is for counting iterations
count_iterations = 0
while areSame(initial_state,final_state)!=True:
entry_one =1000
entry_two = 1000
entry_three = 1000
entry_four = 1000
#this is the shorthand code for finding the index of 0 box , i copied it from stack overflow
index = [(index, row.index(val)) for index, row in enumerate(initial_state) if val in row]
(row_index , column_index) = index[0]
count_iterations += 1
# all possible cases of the 0 box and then appropriate directions are called.
if row_index != 0:
entry_one= moveUp(initial_state,row_index,column_index)
if column_index!=0:
entry_four= moveLeft(initial_state,row_index,column_index)
if column_index != 2:
entry_two= moveRight(initial_state,row_index,column_index)
if row_index != 2:
entry_three = moveDown(initial_state,row_index,column_index)
# h(n) = misplaced tiles + no of iterations
entry_one += count_iterations
entry_two += count_iterations
entry_three += count_iterations
entry_four += count_iterations
# finding the minimum heuristic value
min_entry = min(entry_one,entry_two,entry_three,entry_four)
if min_entry == entry_one:
initial_state[row_index][column_index] , initial_state[row_index-1][column_index]= initial_state[row_index-1][column_index], initial_state[row_index][column_index]
elif min_entry == entry_two:
initial_state[row_index][column_index] , initial_state[row_index][column_index+1] = initial_state[row_index][column_index+1],initial_state[row_index][column_index]
elif min_entry == entry_three:
initial_state[row_index][column_index] , initial_state[row_index+1][column_index] = initial_state[row_index+1][column_index],initial_state[row_index][column_index]
else:
initial_state[row_index][column_index], initial_state[row_index][column_index-1] = initial_state[row_index][column_index-1], initial_state[row_index][column_index]
print(f"intermediate state = {initial_state}")