Pruning with Graphs as Lists
lExample 1:
l[ [a, b], [a, c], [b, d], [c, d], [c,
e], [e, a] ] ==>
l[ [a, b], [a, c], [c, e], [e, a]] ==>
l[ [a, c], [c, e], [e, a] ] (no leaves)
lExample 2:
l[ [a, b], [a, c], [b, d], [c, d], [c, e]] ==>
l[ [a, b], [a, c] ] ==>
l[ ]