new_contents: #! /usr/bin/python3
  import sys
  
  def nqueens(board_width):
  	board = [0]
  	current_row = 0
  	while True:
  		conflict = False
  		
  		for review_index in range(0, current_row):
  			left = board[review_index] - (current_row - review_index)
  			right = board[review_index] + (current_row - review_index);
  			if (board[current_row] == board[review_index] or (left >= 0 and left == board[current_row]) or (right < board_width and right == board[current_row])):
  				conflict = True;
  				break
  	
  		if (current_row == 0 and conflict == False):
  			board.append(0)
  			current_row = 1
  			continue
  
  		if (conflict == True):
  			board[current_row] += 1
  			
  			if (current_row == 0 and board[current_row] == board_width):
  				print("No solution exists for specificed board size.")
  				return None
  			
  			while True:
  				if (board[current_row] == board_width):
  					board[current_row] = 0
  					if (current_row == 0):
  						print("No solution exists for specificed board size.")
  						return None
  					
  					board.pop()
  					current_row -= 1
  					board[current_row] += 1
  					
  				if board[current_row] != board_width:
  					break
  		else:
  			current_row += 1
  			if (current_row == board_width):
  				break
  
  			board.append(0)
  	return board
  
  def print_board(board):
  	if (board == None):
  		return
  
  	board_width = len(board)
  	for row in range(board_width):
  		line_print = []
  		for column in range(board_width):
  			if column == board[row]:
  				line_print.append("Q")
  			else:
  				line_print.append(".")
  		print(line_print)
  
  
  if __name__ == '__main__':
  	default_width = 8
  	for arg in sys.argv:
  		if (arg.isdecimal() and int(arg) > 3):
  			default_width = int(arg)
  			break
  		
  	if (default_width == 8):
  		print("Running algorithm with board size of 8. Specify an alternative Chess board size for N-Queens as a command line argument.")
  	
  	board = nqueens(default_width)
  	print(board)
  	print_board(board)
subject: Add NQueens backtracking search implementation (#504)