Lists, Sets
Sets are great for de-duplicating lists:
>>> deduped = set([1, 1, 2, 3]))
>>> answer = list(deduped)
Except that sets do not maintain order, so we can’t extract the
original order where items appeared; our answer could be
[2, 1, 3], when we want [1, 2, 3].
You need to do the de-duplicating by hand. You could do this like:
result = []
for char in items:
if char not in result:
result.append(char)
return result
This would work, but it would be O(n ** 2) runtime, since, for every item, we’d be looking in the result list (which is a linear operation).
You can solve this by using a set to keep track of what’s seen, and using a list to hold the results:
def deduped(items):
"""Return new list from items with duplicates removed."""
# START SOLUTION
# keep track of items we've seen
seen = set()
# list to hold our answer
result = []
for item in items:
if item not in seen:
result.append(item)
seen.add(item)
return result