Daniel@0: % Do the example in fig 23.4 p479 of Cormen, Leiserson and Rivest (1994)
Daniel@0: 
Daniel@0: u = 1; v = 2; w = 3; x = 4; y = 5; z = 6;
Daniel@0: n = 6;
Daniel@0: dag=zeros(n,n);
Daniel@0: dag(u,[v x])=1;
Daniel@0: dag(v,y)=1;
Daniel@0: dag(w,[y z])=1;
Daniel@0: dag(x,v)=1;
Daniel@0: dag(y,x)=1;
Daniel@0: dag(z,z)=1;
Daniel@0: 
Daniel@0: [d, pre, post, cycle, f, pred] = dfs(dag, [], 1);
Daniel@0: assert(isequal(d, [1 2 9 4 3 10]))
Daniel@0: assert(isequal(f, [8 7 12 5 6 11])
Daniel@0: assert(cycle)
Daniel@0: 
Daniel@0: % Now give it an undirected cyclic graph
Daniel@0: G = mk_2D_lattice(2,2,0);
Daniel@0: % 1 - 3
Daniel@0: % |   |
Daniel@0: % 2 - 4
Daniel@0: [d, pre, post, cycle, f, pred] = dfs(G, [], 0);
Daniel@0: % d = [1 2 4 3]
Daniel@0: assert(cycle)
Daniel@0: 
Daniel@0: % Now break the cycle
Daniel@0: G(1,2)=0; G(2,1)=0;
Daniel@0: [d, pre, post, cycle, f, pred] = dfs(G, [], 0);
Daniel@0: assert(~cycle)