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):
#!/usr/bin/python3
# -*- coding: utf-8 -*-

import sys

def bubble_sort(A):
    for i in range(len(A)):
        for x in range(len(A)-1, i, -1):
            if A[x][1] < A[x-1][1]:
                A[x], A[x-1] = A[x-1], A[x]

def selection_sort(A):
    for i in range(len(A)):
        min_val = A[i][1]
        for x in range(i, len(A)):
            if A[x][1] < min_val:
                min_val = A[x][1]
                min_index = x
        if min_val < A[i][1]:
            A[min_index], A[i] = A[i], A[min_index]

def check_stable(srt_list, org_list):
    prev_val = None
    prev_pos = -1
    for card in srt_list:
        cur_pos = org_list.index(card)
        
        if card[1] == prev_val:
            if cur_pos < prev_pos:
                print('Not Stable')
                return
        prev_val = card[1]
        prev_pos = cur_pos

    print('Stable')


n = int(sys.stdin.readline())
org_list = sys.stdin.readline().split()
_list1 = org_list[:]
_list2 = org_list[:]

bubble_sort(_list1)
selection_sort(_list2)

print(' '.join(_list1))
check_stable(_list1, org_list)
print(' '.join(_list2))
check_stable(_list2, org_list)



Fixed, accepted submission:
#!/usr/bin/python3
# -*- coding: utf-8 -*-

import sys

def bubble_sort(A):
    for i in range(len(A)):
        for x in range(len(A)-1, i, -1):
            if A[x][1] < A[x-1][1]:
                A[x], A[x-1] = A[x-1], A[x]

def selection_sort(A):
    for i in range(len(A)):
        min_val = A[i][1]
        for x in range(i, len(A)):
            if A[x][1] < min_val:
                min_val = A[x][1]
                min_index = x
        if min_val < A[i][1]:
            A[min_index], A[i] = A[i], A[min_index]

def check_stable(srt_list, org_list):
    prev_val = None
    prev_pos = -1
    for card in srt_list:
        cur_pos = org_list.index(card)
        
        if card[1] == prev_val:
            if cur_pos < prev_pos:
                print('Not stable')
                return
        prev_val = card[1]
        prev_pos = cur_pos

    print('Stable')


n = int(sys.stdin.readline())
org_list = sys.stdin.readline().split()
_list1 = org_list[:]
_list2 = org_list[:]

bubble_sort(_list1)
selection_sort(_list2)

print(' '.join(_list1))
check_stable(_list1, org_list)
print(' '.join(_list2))
check_stable(_list2, org_list)