Problem Statement

Free Cell is the solitaire card game that Paul Alfille introduced to the PLATO system in 1978. Jim Horne, at Microsoft, changed the name to FreeCell and reimplemented the game for DOS, then Windows. This version introduced 32000 numbered deals. (The FreeCell FAQ tells this history.) As the game became popular, Jim Horne disclosed the algorithm, and other implementations of FreeCell began to reproduce the Microsoft deals. These deals are numbered from 1 to 32000. Newer versions from Microsoft have 1 million deals, numbered from 1 to 1000000; some implementations allow numbers outside that range. The algorithm uses this linear congruential generator from Microsoft C:

The algorithm follows: Deals can also be checked against FreeCell solutions to 1000000 games. (Summon a video solution, and it displays the initial deal.) Write a program to take a deal number and deal cards in the same order as this algorithm. The program may display the cards with ASCII, with Unicode, by drawing graphics, or any other way. Related tasks:

Let's start with the solution:

include c:\cxpl\codes;                  \intrinsic 'code' declarations
string 0;                               \use zero-terminated string convention
int  RandState;

func Rand;                              \Random number in range 0 to 32767
[RandState:= (214013*RandState + 2531011) & $7FFF_FFFF;
return RandState >> 16;
];

int  Card, Deck(52), Size;
char Suit, Rank;
[RandState:= IntIn(8);                  \seed RNG with number from command line
for Card:= 0 to 52-1 do Deck(Card):= Card; \create array of 52 cards
Rank:= "A23456789TJQK";
Suit:= "CDHS";
Size:= 52;
repeat  Card:= rem(Rand/Size);          \choose a random card
        ChOut(0, Rank(Deck(Card)/4));   \deal it by showing it
        ChOut(0, Suit(rem(0)));
        if rem(Size/8)=5 then CrLf(0) else ChOut(0, ^ );
        Size:= Size-1;                  \one less card in deck
        Deck(Card):= Deck(Size);        \replace dealt card with last card
until   Size = 0;                       \all cards have been dealt
]