Data commit

Task/Monty-Hall-problem/D/monty-hall-problem.d

@@ -0,0 +1,31 @@
+import std.stdio, std.random;
+
+void main() {
+  int switchWins, stayWins;
+
+  while (switchWins + stayWins < 100_000) {
+    immutable carPos = uniform(0, 3);  // Which door is car behind?
+    immutable pickPos = uniform(0, 3);  // Contestant's initial pick.
+    int openPos;  // Which door is opened by Monty Hall?
+
+    // Monty can't open the door you picked or the one with the car
+    // behind it.
+    do {
+      openPos = uniform(0, 3);
+    } while(openPos == pickPos || openPos == carPos);
+
+    int switchPos;
+    // Find position that's not currently picked by contestant and
+    // was not opened by Monty already.
+    for (; pickPos==switchPos || openPos==switchPos; switchPos++) {}
+
+    if (pickPos == carPos)
+      stayWins++;
+    else if (switchPos == carPos)
+      switchWins++;
+    else
+      assert(0);  // Can't happen.
+  }
+
+  writefln("Switching/Staying wins: %d %d", switchWins, stayWins);
+}