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):
def selection(a, n):
    
    cnt = 0
    for i in range(n):
        flag = 0
        minj = i
        for j in range(i+1,n):
            if int(a[j][1]) < int(a[minj][1]):
                minj = j
                flag = 1
        if flag == 1:
            temp = a[minj]
            a[minj] = a[i]
            a[i] = temp
            cnt += 1
    return cnt

def bubble(a, n):
    cnt = 0
    for i in range(n):
        for j in reversed(range(i+1,n)):
            if int(a[j][1]) < int(a[j-1][1]):
                temp = a[j]
                a[j] = a[j-1]
                a[j-1] = temp
                cnt += 1
    return cnt

def print_array(a):
    ans = str(a[0])
    for i in range(1,n):
        ans += ' '+str(a[i])  
    print(ans)

def is_stable(a, b):
    for card1 in range(len(a)):
        for card2 in range(card1+1,len(a)):
            if a[card1][1] == a[card2][1]:
                if b.index(a[card1]) > b.index(a[card2]):
                    return 'Not Stable'
    return 'Stable'

n = int(input())
a = input().split()

bub = a[:]
cnt = bubble(bub, n)   
print_array(bub)
print(is_stable(a, bub))

sel = a[:]
cnt = selection(sel, n)   
print_array(sel)
print(is_stable(a, sel))


Fixed, accepted submission:
# -*- coding: utf-8 -*-
"""
Created on Sat Apr 28 09:21:55 2018
ALDS-1-2c
@author: maezawa
"""

def selection(a, n):
    
    cnt = 0
    for i in range(n):
        flag = 0
        minj = i
        for j in range(i+1,n):
            if int(a[j][1]) < int(a[minj][1]):
                minj = j
                flag = 1
        if flag == 1:
            temp = a[minj]
            a[minj] = a[i]
            a[i] = temp
            cnt += 1
    return cnt

def bubble(a, n):
    cnt = 0
    for i in range(n):
        for j in reversed(range(i+1,n)):
            if int(a[j][1]) < int(a[j-1][1]):
                temp = a[j]
                a[j] = a[j-1]
                a[j-1] = temp
                cnt += 1
    return cnt

def print_array(a):
    ans = str(a[0])
    for i in range(1,n):
        ans += ' '+str(a[i])  
    print(ans)

def is_stable(a, b):
    for card1 in range(len(a)):
        for card2 in range(card1+1,len(a)):
            if a[card1][1] == a[card2][1]:
                if b.index(a[card1]) > b.index(a[card2]):
                    return 'Not stable'
    return 'Stable'

n = int(input())
a = input().split()

bub = a[:]
cnt = bubble(bub, n)   
print_array(bub)
print(is_stable(a, bub))

sel = a[:]
cnt = selection(sel, n)   
print_array(sel)
print(is_stable(a, sel))