exercise on list

[philippe]

Le 08/04/2012 21:04, abd_bela a écrit :
>
>
> without using (loops: for or while)  create  the list of numbers as follow:

whitout loops it's fun :-)

> 1, 2, 2, 3 3 3  4 4 4 4    5 5 5 5 5    ......       9 9 9 9 9  9 9 9 9

easy : build a 9x9 matrix with A(i,j)=i, take the lower triangular part 
of A with tril), rewrite it as a one line list (with :), and keep only 
non zero coefficients :

n=9;
A=(tril(([1:n]')*ones(1:n)))'; B=A(:); C=B(find(B<>0))'

>
> 1 0  2 0 0  3 0 0 0    4 0 0 0 0       .....  9  0 0 0 0  0 0 0 0 0

harder, but based on the same ideas :

n=9;A=-ones(n+1,n+1); A(1,2:n+1)=[1:n]; 
A=triu(A);B=A(:);C=B(find(B<>0))'; C(find(C==-1))=0; C(1)=[]


Philippe.