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/local/bin/python3
# coding: utf-8

def swap(c, i, j):
    t = c[i]
    c[i] = c[j]
    c[j] = t

def bubble_sort(c, f):
    for i in range(len(c) - 1):
        for j in range(i + 1, len(c)):
            # print(i, j)
            if f(c[i]) > f(c[j]):
                swap(c, i, j)
    return c

def selection_sort(c, f):
    for i in range(len(c)):
        minj = i
        for j in range(i, len(c)):
            if f(c[j]) < f(c[minj]):
                minj = j
        swap(c, i, minj)
    return c

def to_group(c):
    b = {}
    for i in c:
        if not(i[1] in b):
            b[i[1]] = [i]
        else:
            b[i[1]] = b[i[1]] + [i]
    return b

def is_stable(c, s): 
    bc = to_group(c)
    bs = to_group(s(c, lambda x: x[1]))
    # print(bc)
    # print(bs)
    for k in bc:
        if bc[k] != bs[k]:
            return "Not stable"
    return "Stable"

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

print(" ".join(bubble_sort(c, lambda x: x[1])))
print(is_stable(c, bubble_sort))

print(" ".join(selection_sort(c, lambda x: x[1])))
print(is_stable(c, selection_sort))


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

def swap(c, i, j):
    t = c[i]
    c[i] = c[j]
    c[j] = t

def bubble_sort(cs, f):
    c = cs[:]
    for i in range(len(c) - 1):
        for j in range(len(c) - 1, i, -1):
            if f(c[j - 1]) > f(c[j]):
                swap(c, j - 1, j)
            # print(i, j, c)
    return c

def selection_sort(cs, f):
    c = cs[:]
    for i in range(len(c)):
        minj = i
        for j in range(i, len(c)):
            if f(c[j]) < f(c[minj]):
                minj = j
        swap(c, i, minj)
        # print(c)
    return c

def to_group(c):
    b = {}
    for i in c:
        if not(i[1] in b):
            b[i[1]] = [i]
        else:
            b[i[1]] = b[i[1]] + [i]
    return b

def is_stable(c, s): 
    bc = to_group(c)
    bs = to_group(s(c, lambda x: x[1]))
    # print(bc)
    # print(bs)
    for k in bc:
        if bc[k] != bs[k]:
            return "Not stable"
    return "Stable"

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

print(" ".join(bubble_sort(c, lambda x: x[1])))
print(is_stable(c, bubble_sort))

print(" ".join(selection_sort(c, lambda x: x[1])))
print(is_stable(c, selection_sort))