Functions 6 - exercises with sets

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Exercise - syllabs

Write a function syllabs which given a string word made by only bisyllabs and a set found, finds all the distinct bisyllabs and puts them into the set found.

  • NOTE: the function syllabs return NOTHING !

Example 1:

>>> found = set()
>>> syllabs("banana", found)
>>> found
{'an', 'ba'}

Example 2:

>>> found = set()
>>> syllabs("parariraparara", found)
>>> found
{'ri', 'ra', 'pa'}
Show solution

# write here

Exercise - distinguish

✪✪ Write a function distinguish which given a list big_list containing sublists of two characters each, RETURN a NEW LIST containing all the distinct sublists (ignoring the duplicated sublists)

  • the returned list must have the elements in the same order in which they were found in big_list

  • to know fast whether a sublist was already found, use a set

  • DO NOT search in lists (so no count, index, in in lists - they’re slow!)

  • DO NOT remove from lists (so no remove from lists - it’s slow!)

  • HINT: lists are mutable, can we place them in a set? If it’s not possible, what can we do?


>>> big_list = [ ['d','d'],['a','b'],['d','d'],['c','a'],['c','a'],['d','d'],['a','b'] ]
>>> distinguish( big_list)
[['d', 'd'], ['a', 'b'], ['c', 'a']]
#NOTE: variable big_list MUST NOT be modified:
>>> big_list
[ ['d','d'],['a','b'],['d','d'],['c','a'],['c','a'],['d','d'],['a','b'] ]
Show solution
# write here

Exercise - intersectron


Given a list sets containing an arbitrary number of sets, RETURN a NEW set which contains the elements common to all sets.

To solve the exercise, you can intersecate a set at a time with a for cycle (slow) or with the technique described here (short and fast).

  • try to solve it in both ways

  • BEWARE of the empty list!

  • your code must work with any number of sets (the image is just an example)

Show solution
def inter_for(sets):

    raise Exception('TODO IMPLEMENT ME !')

assert inter_for([]) == set()
assert inter_for([set(),set()]) == set()
assert inter_for([set(),set(),set()]) == set()
assert inter_for([{'a'},{'a'},{'a'}]) == {'a'}
assert inter_for([{'a','b'},{'b'},{'b'}]) == {'b'}
assert inter_for([{'a'},{'a','b'},{'a'}]) == {'a'}
assert inter_for([{'c'},{'c'},{'c','b'}]) == {'c'}
assert inter_for([{'a','b'},{'a','b'},{'a','b'}]) == {'a','b'}
assert inter_for([{'a','b','c'},{'a','b','c','d'},{'b','c','d'}, {'b','c'}]) == {'b','c'}
# check we didn't modify the input sets
s = {'a','b'}
assert inter_for([s,{'b','c'}]) == {'b'}
assert s == {'a','b'}
Show solution
def inter_fast(sets):

    raise Exception('TODO IMPLEMENT ME !')

assert inter_fast([]) == set()
assert inter_fast([set(),set()]) == set()
assert inter_fast([set(),set(),set()]) == set()
assert inter_fast([{'a'},{'a'},{'a'}]) == {'a'}
assert inter_fast([{'a','b'},{'b'},{'b'}]) == {'b'}
assert inter_fast([{'a'},{'a','b'},{'a'}]) == {'a'}
assert inter_fast([{'c'},{'c'},{'c','b'}]) == {'c'}
assert inter_fast([{'a','b'},{'a','b'},{'a','b'}]) == {'a','b'}
assert inter_fast([{'a','b','c'},{'a','b','c','d'},{'b','c','d'}, {'b','c'}]) == {'b','c'}
# check we didn't modify the input sets
s = {'a','b'}
assert inter_fast([s,{'b','c'}]) == {'b'}
assert s == {'a','b'}
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