def _trivial(L):
# L is empty or has only one (mapping, weight) pair. If there is a
# pair, we may still need to multiply the mapping by its weight.
assert len(L) <= 1
if len(L) == 0:
return IFBucket()
[(result, weight)] = L
if weight != 1:
dummy, result = weightedUnion(IFBucket(), result, 0, weight)
return result
def mass_weightedUnion(L):
"A list of (mapping, weight) pairs -> their weightedUnion IFBucket."
if len(L) < 2:
return _trivial(L)
# Balance unions as closely as possible, smallest to largest.
merge = NBest(len(L))
for x, weight in L:
merge.add((x, weight), len(x))
while len(merge) > 1:
# Merge the two smallest so far, and add back to the queue.
(x, wx), dummy = merge.pop_smallest()
(y, wy), dummy = merge.pop_smallest()
dummy, z = weightedUnion(x, y, wx, wy)
merge.add((z, 1), len(z))
(result, weight), dummy = merge.pop_smallest()
return result
