N queen

def backtrack(Q,r):
if r==len(Q):
print_chess_board(Q)
else:
for j in range(len(Q)):
legal=True
for i in range(r):
if((Q[i]==j)or(Q[i]==j+r-i)or(Q[i]==j-r+i)):
legal=False
if legal:
Q[r]=j
backtrack(Q,r+1)

def print_chess_board(d):
chess_board=" "
for i in range(len(d)):
for j in range(len(d)):
if j==d[i]:
chess_board+=" Q "
else:
chess_board+=" - "
chess_board+=" \n "
print(chess_board)

def create_chess_board(size):
mat=[]
for i in range(size):
mat.append(0)
return mat
size=int(input("IP your board size "))
backtrack(create_chess_board(size),0)