Data commit

Task/100-prisoners/XPL0/100-prisoners.xpl0

@@ -0,0 +1,58 @@
+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);
+]