def findRings(graph):
"""
a very simple ring detection algorightm to identify 5, and 6 member aromatic rings
A <- head
/ \
B C <- tier 1
| |
D E <- tier 2
\ /
F <- tier 3, ring closure (6 member-ring)
A <- head
/ \
B C <- tier 1
| |
D---E <- tier 2, ring closure (5-member ring)
A <- head
|
B <- tier 1
/ \
C---D <- tier 2 # SPURIOUS, RECOGNIZED BUT NOT COUNTED
"""
# TODO add a planarity check?
rings5 = []
rings6 = []
if DEBUG: print "- starting ring detection..."
for head in graph.keys():
tier1 = graph[head]
tier2 = []
tier3 = []
# populate tier2
for node1 in tier1:
for tmp in graph[node1]:
if not tmp == head and not tmp in tier2 and (not tmp in tier1) :
tier2.append(tmp)
# populate tier3
for node2 in tier2:
for tmp in graph[node2]:
if (not tmp == head) and (not tmp in tier2) and (not tmp in tier1) and (not tmp in tier3):
tier3.append(tmp)
# 6 member rings
for x in tier3:
candidate = []
for c in tier2:
if x in graph[c]:
if not c in candidate:
candidate.append(c)
if len(candidate) >1:
r6 = [ head ]
r6.append(x)
r6 += candidate
for c in candidate:
r6 += hf.intersect( graph[head], graph[c])
r6.sort()
if not r6 in rings6:
rings6.append( r6 )
if DEBUG: print " 6member!", r6
break
# 5 member rings
for c1 in tier2:
for c2 in tier2:
if not c1 == c2:
if (c2 in graph[c1]) and (c1 in graph[c2]):
is_3_ring = False
for k in graph[c1]:
if k in graph[c2]:
is_3_ring =True
if DEBUG: print " [ ...catched a cycle_3... ]"
break
if not is_3_ring :
r5 = [ head ]
r5.append(c1)
r5.append(c2)
r5 += hf.intersect( graph[head], graph[c1])
r5 += hf.intersect( graph[head], graph[c2])
r5.sort()
if not r5 in rings5:
if DEBUG: print " 5member ring!",r5
rings5.append(r5)
break
return rings5, rings6
