find commun neighbor of matrix

Hello, I have a graph which is represented by this matrix A =[0 1 0 1; 1 0 0 0; 0 1 0 0; 1 0 1 0;]

i went to search the no nodes of matrix which have a commun neighbor, for exemple node 1 is connected with [2,4] and node 2 is connected with [1, 4] so nodes 1 and 2 have a commun neighbor which is node 4

can you Help me PLEASE? ^-^

[Rik]

Have a read here and here. It will greatly improve your chances of getting an answer.

[KSSV]

What is a node? Why and how they are connected? On what context this question is?

[Santhana Raj]

If the matrix you have given is a node connectivity matrix, doesn't this has to be symmetric??

[Walter Roberson]

Not for directed graphs it does not need to be symmetric.

"having a common neighbor" in a directed graph situation does not promise that the nodes are reachable from each other. For example node 4 might have directed links only towards nodes 1 and 2, with there being way to get from node 1 to node 2 by way of node 4.

Answer 1

[Santhana Raj]

From my understanding of nodes,

A =[0 1 0 1; 1 0 0 0; 0 1 0 0; 1 0 1 0;]
h=zeros(4);
for i=1:4
    [~,H]=find(A(i,:)==1);
    h(i,1:length(H))=H;
end
neigh=[];
for i=1:4
    if numel(nonzeros(h(:)==i))>1
        neigh=[neigh i];
    end
end

this seems to work.