Problem:
Let's arrange a deck of cards. There are totally 36 cards of 4 suits(S, H, C, D) and 9 values (1, 2, ... 9). For example, 'eight of heart' is represented by H8 and 'one of diamonds' is represented by D1.  Your task is to write a program which sorts a given set of cards in ascending order by their values using the Bubble Sort algorithms and the Selection Sort algorithm respectively. These algorithms should be based on the following pseudocode:                 BubbleSort(C) 1 for i = 0 to C.length-1 2     for j = C.length-1 downto i+1 3         if C[j].value < C[j-1].value 4             swap C[j] and C[j-1]                 SelectionSort(C) 1 for i = 0 to C.length-1 2     mini = i 3     for j = i to C.length-1 4         if C[j].value < C[mini].value 5             mini = j 6     swap C[i] and C[mini]   Note that, indices for array elements are based on 0-origin.  For each algorithm, report the stability of the output for the given input (instance). Here, 'stability of the output' means that: cards with the same value appear in the output in the same order as they do in the input (instance).

Incorrect submission (verdict: Wrong Answer):
# -*- coding: utf-8 -*-


def bubble_sort(cards, num):
    for left in range(num-1):
        for right in range(left+1, num):
            if cards[right][1] < cards[left][1]:
                cards[left], cards[right] = cards[right], cards[left]

    print(list_to_str(cards))


def selection_sort(cards, num):
    for head in range(num):
        min_i = head

        for target in range(head+1, num):
            if cards[target][1] < cards[min_i][1]:
                min_i = target
        cards[head], cards[min_i] = cards[min_i], cards[head]

    print(list_to_str(cards))


def is_stable(before, after, num):
    for i in range(num):
        for j in range(i+1, num):
            for a in range(num):
                for b in range(a+1, num):
                    if before[i][1] == before[j][1]\
                    and before[i] == after[b]\
                    and before[j] == after[a]:
                        print('Not stable')
    print('Stable')


def list_to_str(l, delimiter=' '):
    # The default delimiter is one space.
    return delimiter.join([str(v) for v in l])


if __name__ == '__main__':
    num = int(input())
    cards = input().split()
    cards_for_bubble = cards.copy()
    cards_for_selection = cards.copy()

    bubble_sort(cards_for_bubble, num)
    is_stable(cards, cards_for_bubble, num)

    selection_sort(cards_for_selection, num)
    is_stable(cards, cards_for_selection, num)

Fixed, accepted submission:
# -*- coding: utf-8 -*-


def bubble_sort(cards, num):
    for tail in range(num-1, 0, -1):
        for right in range(0, tail):
            left = right + 1
            if cards[left][1] < cards[right][1]:
                cards[right], cards[left] = cards[left], cards[right]

    print(list_to_str(cards))


def selection_sort(cards, num):
    for head in range(num):
        min_i = head

        for target in range(head+1, num):
            if cards[target][1] < cards[min_i][1]:
                min_i = target
        cards[head], cards[min_i] = cards[min_i], cards[head]

    print(list_to_str(cards))


def is_stable(before, after, num):
    for i in range(num):
        for j in range(i+1, num):
            for a in range(num):
                for b in range(a+1, num):
                    if before[i][1] == before[j][1]\
                    and before[i] == after[b]\
                    and before[j] == after[a]:
                        return 'Not stable'
    return 'Stable'


def list_to_str(l, delimiter=' '):
    # The default delimiter is one space.
    return delimiter.join([str(v) for v in l])


if __name__ == '__main__':
    num = int(input())
    cards = input().split()
    cards_for_bubble = cards.copy()
    cards_for_selection = cards.copy()

    bubble_sort(cards_for_bubble, num)
    print(is_stable(cards, cards_for_bubble, num))

    selection_sort(cards_for_selection, num)
    print(is_stable(cards, cards_for_selection, num))