list1.py

# A. match_ends
# Given a list of strings, return the count of the number of
# strings where the string length is 2 or more and the first
# and last chars of the string are the same.
# Note: python does not have a ++ operator, but += works.
def match_ends(words):
    n = 0
    for word in words:
        if len(word) >= 2 and word[0] == word[len(word) - 1]:
            n += 1
    return n


# B. front_x
# Given a list of strings, return a list with the strings
# in sorted order, except group all the strings that begin with 'x' first.
# e.g. ['mix', 'xyz', 'apple', 'xanadu', 'aardvark'] yields
# ['xanadu', 'xyz', 'aardvark', 'apple', 'mix']
# Hint: this can be done by making 2 lists and sorting each of them
# before combining them.
def front_x(words):
    listx = []
    listnorm = []
    for word in words:
        if word[0] == 'x':
            listx.append(word)
        else:
            listnorm.append(word)

    return sorted(listx) + sorted(listnorm)


# C. sort_last
# Given a list of non-empty tuples, return a list sorted in increasing
# order by the last element in each tuple.
# e.g. [(1, 7), (1, 3), (3, 4, 5), (2, 2)] yields
# [(2, 2), (1, 3), (3, 4, 5), (1, 7)]
# Hint: use a custom key= function to extract the last element form each tuple.
def sort_last(tuples):
    endings = []
    res = []
    for e in tuples:
        endings.append(e[-1])
    endings.sort()
    for ending in endings:
        for tup in tuples:
            if tup[-1] == ending:
                res.append(tup)
    return res



# Simple provided test() function used in main() to print
# what each function returns vs. what it's supposed to return.
def test(got, expected):
    if got == expected:
        prefix = ' OK '
    else:
        prefix = '  X '
    print('%s got: %s expected: %s' % (prefix, repr(got), repr(expected)))


# Calls the above functions with interesting inputs.
def main():
    print('match_ends')
    test(match_ends(['aba', 'xyz', 'aa', 'x', 'bbb']), 3)
    test(match_ends(['', 'x', 'xy', 'xyx', 'xx']), 2)
    test(match_ends(['aaa', 'be', 'abc', 'hello']), 1)

    print()
    print('front_x')
    test(front_x(['bbb', 'ccc', 'axx', 'xzz', 'xaa']),
         ['xaa', 'xzz', 'axx', 'bbb', 'ccc'])
    test(front_x(['ccc', 'bbb', 'aaa', 'xcc', 'xaa']),
         ['xaa', 'xcc', 'aaa', 'bbb', 'ccc'])
    test(front_x(['mix', 'xyz', 'apple', 'xanadu', 'aardvark']),
         ['xanadu', 'xyz', 'aardvark', 'apple', 'mix'])

    print()
    print('sort_last')
    test(sort_last([(1, 3), (3, 2), (2, 1)]),
         [(2, 1), (3, 2), (1, 3)])
    test(sort_last([(2, 3), (1, 2), (3, 1)]),
         [(3, 1), (1, 2), (2, 3)])
    test(sort_last([(1, 7), (1, 3), (3, 4, 5), (2, 2)]),
         [(2, 2), (1, 3), (3, 4, 5), (1, 7)])


if __name__ == '__main__':
    main()