CSP ( CONSTRAINTS SATISFACTION )

global N
N = int(input("Enter number of queens: "))

def printSolution(board):
    for i in range(N):
        for j in range(N):
            print(board[i][j], end=" ")
        print()

def isSafe(board, row, col):
    # Check if there is a queen in the current row
    for i in range(col):
        if board[row][i] == 'Q':
            return False

    # Check upper diagonal on left side
    for i, j in zip(range(row, -1, -1), range(col, -1, -1)):
        if board[i][j] == 'Q':
            return False

    # Check lower diagonal on left side
    for i, j in zip(range(row, N, 1), range(col, -1, -1)):
        if board[i][j] == 'Q':
            return False

    return True

def solveNQUtil(board, col):
    if col >= N:
        return True

    for i in range(N):
        if isSafe(board, i, col):
            board[i][col] = 'Q'
            if solveNQUtil(board, col + 1):
                return True
            board[i][col] = 0

    return False

def solveNQ():
    board = [['.' for i in range(N)] for j in range(N)]
    if solveNQUtil(board, 0) == False:
        print("Solution does not exist")
        return False

    print("Queens Placement:")
    printSolution(board)
    return True

solveNQ()