function [A u] = place_N_queens_random(N)
% this function places N queens on random places
% on the NxN board, and returns an NxN matrix with N queens

A = zeros(N);
u = 0;      % current number of queens in the matrix
    while u ~= N
        p=randperm(N);
        p=p(1);
        q=randperm(N);
        q=q(1);
        A(p, q) = 1;
        u = numel(find(A));
    end
end