[perl-python] exercise: partition a list by equivalence

[Paul McGuire]

Please consider my submission also (Python 2.3-compatible).

-- Paul McGuire

.    import sets
.
.    input = [[1, 2], [3, 4], [2, 3], [4, 5]]
.    input = [[1, 2], [3, 4], [4, 5]]
.    input = [[1, 2],[2,1], [3, 4], [4, 5],[2,2],[2,3],[6,6]]
.
.    def merge(pairings):
.        ret = []
.        for a,b in pairings:
.            s1 = None
.            s2 = None
.            for s in ret:
.                if a in s or b in s:
.                    if s1 is None:
.                        s1 = s
.                    else:
.                        s2 = s
.                        break
.            else:
.                for s in ret:
.                    if a in s:
.                        s.add(b)
.                        break
.                    elif b in s:
.                        s.add(a)
.                        break
.                else:
.                    ret.append(sets.Set([a,b]))
.                continue
.            ret.remove(s1)
.            ret.remove(s2)
.            ret.append(s1.union(s2))
.
.        return [list(s) for s in ret]
.                
.    print merge(input)