C++ solution to the N-queens problem

nqueens.cpp

// nqueens.cpp
// Aswin van Woudenberg

#include <iostream>
#include <cstdlib>

bool issafe(int *rows, int i)
{
	for (int k=0; k<i; k++)
		if (rows[i] == rows[k] || abs(rows[i]-rows[k]) == i-k)
			return false;
	return true;
}

void println(int n)
{
	std::cout << "+";
	for (int c=0; c<n; c++)
		std::cout << "-+";
	std::cout << std::endl;
}

void printsol(int *rows, int n)
{
	println(n);
	for (int r=0; r<n; r++)
	{
		std::cout << "|";
		for (int c=0; c<n; c++)
			if (rows[r] == c)
				std::cout << "Q|";
			else
				std::cout << " |";
		std::cout << std::endl;
		println(n);
	}
	std::cout << std::endl;
}

void nqueens(int *rows, int n, int i)
{
	if (issafe(rows, i-1))
		if (i == n)
			printsol(rows, n);
		else
			for (int k=0; k<n; k++)
			{
				rows[i] = k;
				nqueens(rows, n, i+1);
			}
}

void nqueens(int n)
{
	int *rows;
	rows = new int[n];
	nqueens(rows, n, 0);
	delete [] rows;
}

int main(int argc, char *argv[])
{
	int n; // number of queens

	if (argc == 1)
		std::cout << "Usage: " << argv[0] << " <number_of_queens>" << std::endl;
	else
	{
		n = atoi(argv[1]);
		if (n == 0)
			std::cout << "No valid number of queens entered!" << std::endl;
		else
			nqueens(n);
	}
	return 0;
}