#!/usr/bin/env python

coding: utf-8

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def isSafe(board, row, col):
# Check column for any queen in the same column
for i in range(row):
if board[i][col] == 'Q':
return False

# Check upper-left diagonal
i, j = row, col
while i >= 0 and j >= 0:
    if board[i][j] == 'Q':
        return False
    i -= 1
    j -= 1

# Check upper-right diagonal
i, j = row, col
while i >= 0 and j < len(board):
    if board[i][j] == 'Q':
        return False
    i -= 1
    j += 1

return True

def printBoard(board):
for row in board:
print(" ".join(row))
print()

def placeQueens(board, row):
# Base case: All queens are placed
if row == len(board):
printBoard(board)
return True

# Try placing queen in each column for current row
for col in range(len(board)):
    if isSafe(board, row, col):
        # Place queen
        board[row][col] = 'Q'

        # Recur to place the rest of the queens
        if placeQueens(board, row + 1):
            return True  # Stop after finding the first solution

        # Backtrack if placing queen here doesn't lead to a solution
        board[row][col] = '.'

return False

def solveNQueens(n):
# Initialize board with '.' and place the first queen at top-left corner
board = [['.' for _ in range(n)] for _ in range(n)]
board[0][0] = 'Q' # Place the first queen in the top-left

# Start placing the remaining queens
if not placeQueens(board, 1):  # Start from the second row
    print("No solution found")

Example usage for a 4x4 board

solveNQueens(8)

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