52 lines
1.4 KiB
Matlab
52 lines
1.4 KiB
Matlab
% Support function for tarjan.m
|
|
% "Performs a single depth-first search of the graph, finding all
|
|
% successors from the node vi, and reporting all strongly connected
|
|
% components of that subgraph."
|
|
% See: http://en.wikipedia.org/wiki/Tarjan's_strongly_connected_components_algorithm
|
|
%
|
|
% INPUTs: start node, vi;
|
|
% graph structure (list), L
|
|
% tarjan.m variables to update: S, ind, v, GSCC
|
|
% OUTPUTs: updated tarjan.m variables: S, ind, v, GSCC
|
|
%
|
|
% Note: Contains recursion.
|
|
% Other routines used: strongConnComp.m
|
|
% GB: last updated, Sep 22 2012
|
|
|
|
function [GSCC,S,ind,v]=strongConnComp(vi,S,ind,v,L,GSCC)
|
|
|
|
|
|
v(vi).index = ind; % Set the depth index for vi
|
|
v(vi).lowlink = ind;
|
|
ind = ind + 1;
|
|
|
|
S = [vi S]; % Push vi on the stack
|
|
|
|
for ll=1:length(L{vi})
|
|
vj = L{vi}(ll); % Consider successors of vi
|
|
|
|
if isempty(v(vj).index) % Was successor vj visited?
|
|
|
|
[GSCC,S,ind,v]=strongConnComp(vj,S,ind,v,L,GSCC); % Recursion
|
|
v(vi).lowlink = min([v(vi).lowlink, v(vj).lowlink]);
|
|
|
|
elseif not(isempty(find(S==vj))) % Is vj on the stack?
|
|
v(vi).lowlink = min([v(vi).lowlink, v(vj).index]);
|
|
|
|
end
|
|
end
|
|
|
|
|
|
if v(vi).lowlink == v(vi).index % Is v the root of an SCC?
|
|
|
|
SCC = [vi];
|
|
while 1
|
|
vj = S(1); S = S(2:length(S));
|
|
SCC = [SCC vj];
|
|
|
|
if vj==vi; SCC = unique(SCC); break; end
|
|
end
|
|
|
|
GSCC{length(GSCC)+1} = SCC;
|
|
|
|
end |