At Codebar, I found a challenge online at CodeAbbey that asked you to create a program that would tell you the value of any hand in blackjack, and whether you're bust. If you've never played the game, the aim is to get as close to 21 without going over, where picture cards count as 10, and aces can count as either 1 or 11, depending on what's better for you.
So, if you run this, you can input your hand, and it will give you the statistical likelihood of going over 21 with the next draw. It takes into account the number of cards left in the deck, their values, and whether you're holding an ace or not. After that, you can also put in the cards you know other players hold. Then, it will give an updated statistical likelihood.
There have been a number of changes since I wrote the Codebar version, but the key thing to note is: