findConnCompI.m

function comp=findConnCompI(A,i)
%FINDCONNCOMPI Find the connected component to which node "i" belongs to
% @input A, NxN adjacency matrix
% @input i, a node number to search for
% @output comp, a list of nodes of the connected component of 'i'
%
% Note: Only works for undirected graphs.
% Other functions used: kneighbors.m

% Update: minor optimizations

% IB: last updated, 3/23/14

neigh1=(kneighbors(A,i,1))';   % all neighbors of "i" 1 link away
neigh1=unique([neigh1;  i]);    % add i to its own component

while 1
    len0=length(neigh1);    
    neigh2 = cell(len0, 1);
    for j=1:len0
        neigh2{j}=(kneighbors(A,neigh1(j),1))';        
    end
    neigh1=unique([neigh1; cell2mat(neigh2)]);   % merge neigh1 and neigh2
    if len0==length(neigh1)  % if no new neighbors found, return component
        comp=neigh1;
        return
    end
    
end

end  % end of function