Task: 21 game
C: 



#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>
#include <stdlib.h>
#include <time.h>


#if __STDC_VERSION__ >= 199901L || _MSC_VER >= 1800
#include <stdbool.h>
#else
#define bool int
#define true  1
#define false 0
#endif

#define GOAL               21
#define NUMBER_OF_PLAYERS   2
#define MIN_MOVE            1
#define MAX_MOVE            3
#define BUFFER_SIZE       256

#define _(STRING) STRING



static char DESCRIPTION[] = 
    "21 Game                                                          \n"
    "                                                                 \n"
    "21 is a two player game, the game is played by choosing a number \n"
    "(1, 2, or 3) to be added to the running total. The game is won by\n"
    "the player whose chosen number causes the running total to reach \n"
    "exactly 21. The running total starts at zero.                    \n\n";

static int total;


void update(char* player, int move)
{
    printf("%8s:  %d = %d + %d\n\n", player, total + move, total, move);
    total += move;
    if (total == GOAL)
        printf(_("The winner is %s.\n\n"), player);
}


int ai()
{

#if GOAL < 32 && MIN_MOVE == 1 && MAX_MOVE == 3
    static const int precomputed[] = { 1, 1, 3, 2, 1, 1, 3, 2, 1, 1, 3, 2, 1, 1,
        3, 2, 1, 1, 3, 2, 1, 1, 3, 2, 1, 1, 3, 2, 1, 1, 3 };
    update(_("ai"), precomputed[total]);
#elif MIN_MOVE == 1 && MAX_MOVE == 3
    static const int precomputed[] = { 1, 1, 3, 2};
    update(_("ai"), precomputed[total % (MAX_MOVE + 1)]);
#else
    int i;
    int move = 1;
    for (i = MIN_MOVE; i <= MAX_MOVE; i++)
        if ((total + i - 1) % (MAX_MOVE + 1) == 0)
            move = i;
    for (i = MIN_MOVE; i <= MAX_MOVE; i++)
        if (total + i == GOAL)
            move = i;
    update(_("ai"), move);
#endif
}


void human(void)
{
    char buffer[BUFFER_SIZE];
    int move;
 
    while ( printf(_("enter your move to play (or enter 0 to exit game): ")),
            fgets(buffer, BUFFER_SIZE, stdin), 
            sscanf(buffer, "%d", &move) != 1 ||
            (move && (move < MIN_MOVE || move > MAX_MOVE || total+move > GOAL)))
        puts(_("\nYour answer is not a valid choice.\n"));
    putchar('\n');
    if (!move) exit(EXIT_SUCCESS);
    update(_("human"), move);
}


int main(int argc, char* argv[])
{
    srand(time(NULL));
    puts(_(DESCRIPTION));
    while (true)
    {
        puts(_("\n---- NEW GAME ----\n"));
        puts(_("\nThe running total is currently zero.\n"));
        total = 0;

        if (rand() % NUMBER_OF_PLAYERS)
        {
            puts(_("The first move is AI move.\n"));
            ai();
        }
        else
            puts(_("The first move is human move.\n"));

        while (total < GOAL)
        {
            human();
            ai();
        }
    }
}

Python: from random import randint
def start():
	game_count=0
	print("Enter q to quit at any time.\nThe computer will choose first.\nRunning total is now {}".format(game_count))
	roundno=1
	while game_count<21:
		print("\nROUND {}: \n".format(roundno))
		t = select_count(game_count)
		game_count = game_count+t
		print("Running total is now {}\n".format(game_count))
		if game_count>=21:
			print("So, commiserations, the computer has won!")
			return 0
		t = request_count()
		if not t:
			print('OK,quitting the game')
			return -1
		game_count = game_count+t
		print("Running total is now {}\n".format(game_count))
		if game_count>=21:
			print("So, congratulations, you've won!")
			return 1
		roundno+=1

def select_count(game_count):
	
	if game_count<18:
		t= randint(1,3)
	else:
		t = 21-game_count
	print("The computer chooses {}".format(t))
	return t

def request_count():
	
	t=""
	while True:
		try:
			t = raw_input('Your choice 1 to 3 :')
			if int(t) in [1,2,3]:
				return int(t)
			else:
				print("Out of range, try again")
		except:
			if t=="q":
				return None
			else:
				print("Invalid Entry, try again")

c=0
m=0
r=True
while r:
	o = start()
	if o==-1:
		break
	else:
		c+=1 if o==0 else 0
		m+=1 if o==1 else 0
	print("Computer wins {0} game, human wins {1} games".format(c,m))
	t = raw_input("Another game?(press y to continue):")
	r = (t=="y")