On Jun 11, 6:23 pm, Mensanator <mensana...@aol.com> wrote:
> Removing the duplicates could be a big problem.
It is fairly easy to ignore duplicates in a sorted list:
<pre>
from itertools import groupby
def unique(ordered):
"""Yield the unique elements from a sorted iterable.
"""
for key,_ in groupby(ordered):
yield key
</pre>
Combining this with some ideas of others, we have a simple, complete
solution:
<pre>
def intersect(*ascendingSeqs):
"""Yield the intersection of zero or more ascending iterables.
"""
N=len(ascendingSeqs)
if N==0:
return
unq = [unique(s) for s in ascendingSeqs]
val = [u.next() for u in unq]
while True:
for i in range(N):
while val[i-1] > val[i]:
val[i] = unq[i].next()
if val[0]==val[-1]:
yield val[0]
val[-1] = unq[-1].next()
</pre>
This works with empty arg-lists; combinations of empty, infinite and
finite iterators; iterators with duplicate elements; etc. The only
requirement is that all iterators are sorted ascending.
-- FC
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