Source code in the xpl0 programming language

int     Drawer(100);

proc KShuffle;          \Randomly rearrange the cards in the drawers
\(Woe unto thee if Stattolo shuffle is used instead of Knuth shuffle.)
int  I, J, T;
[for I:= 100-1 downto 1 do
    [J:= Ran(I+1);      \range [0..I]
    T:= Drawer(I);  Drawer(I):= Drawer(J);  Drawer(J):= T;
    ];
];

func Stategy2;          \Return 'true' if stragegy succeeds
int  Prisoner, Card, Try;
[for Prisoner:= 1 to 100 do
   [Card:= Drawer(Prisoner-1);
   Try:= 1;
   loop [if Card = Prisoner then quit;
        if Try >= 50 then return false;
        Card:= Drawer(Card-1);
        Try:= Try+1;
        ];
    ];
return true;
];

func Stategy1;          \Return 'true' if stragegy succeeds
int  Prisoner, I, D(100);
[for Prisoner:= 1 to 100 do
   loop [for I:= 0 to 100-1 do D(I):= I+1;
        KShuffle;
        for I:= 1 to 50 do
            if Drawer(D(I-1)) = Prisoner then quit;
        return false;
        ];
return true;
];

proc Strategy(S);
int  S, I, Sample;
real Successes;
[Successes:= 0.;
for Sample:= 1 to 100_000 do
    [for I:= 0 to 100-1 do Drawer(I):= I+1;
    KShuffle;
    case S of
     1: if Stategy1 then Successes:= Successes + 1.;
     2: if Stategy2 then Successes:= Successes + 1.
    other [];
    ];
RlOut(0, Successes/100_000.*100.);  Text(0, "%^m^j");
];

[Format(3, 12);
Text(0, "Random strategy success rate:  ");
Strategy(1);
Text(0, "Optimal strategy success rate: ");
Strategy(2);
]