Understanding - Advanced, exercise 14

Text

The variable my_mat_l contains a list of integers, each being a 0-9 digit (e.g. [0, 0, 0, 0, 1, 2, 3, 4, 5, 6]), and the variable my_fn contains a string of a family name in lower case. Study the execution of the following functions when they are called as follows: run(my_fn, my_mat_l).

def run(fn, mat_l):
    tot = 0 - len(fn)
    for n in mat_l:
        tot = tot + n

    return work(fn[0:tot], tot)


def work(s, n):
    if n > len(s):
        n = len(s)

    l = list()
    for c in s:
        if c not in l:
            l.append(c)
        else:
            n = n - 1

    idx = len(l) - n

    if idx < len(l) / 2:
        cur1 = l[idx]
        cur2 = l[n - 1]

        if cur1 > cur2:
            l.remove(cur1)
            l.remove(cur2)
            l.insert(idx, cur2)
            l.insert(n - 1, cur1)

        return work("".join(l), n - 1)
    else:
        return s

Hints

The function run preprocess the input string according to the integers in the input list. Then, the recursive function work is called, which manipulates the input string and then applies some swaps.

Additional material

The runnable Python file is available online. You can run it executing the command python exercise_14.py in a shell, and then following the instructions on screen to specify the intended input.