Data commit

Task/Monty-Hall-problem/Dart/monty-hall-problem.dart

@@ -0,0 +1,83 @@
+int rand(int max) => (Math.random()*max).toInt();
+
+class Game {
+  int _prize;
+  int _open;
+  int _chosen;
+
+  Game() {
+    _prize=rand(3);
+    _open=null;
+    _chosen=null;
+  }
+
+  void choose(int door) {
+    _chosen=door;
+  }
+
+  void reveal() {
+    if(_prize==_chosen) {
+      int toopen=rand(2);
+      if (toopen>=_prize)
+        toopen++;
+      _open=toopen;
+    } else {
+      for(int i=0;i<3;i++)
+        if(_prize!=i && _chosen!=i) {
+          _open=i;
+          break;
+        }
+    }
+  }
+
+  void change() {
+    for(int i=0;i<3;i++)
+      if(_chosen!=i && _open!=i) {
+        _chosen=i;
+        break;
+      }
+  }
+
+  bool hasWon() => _prize==_chosen;
+
+  String toString() {
+    String res="Prize is behind door $_prize";
+    if(_chosen!=null) res+=", player has chosen door $_chosen";
+    if(_open!=null) res+=", door $_open is open";
+    return res;
+  }
+}
+
+void play(int count, bool swap) {
+  int wins=0;
+
+  for(int i=0;i<count;i++) {
+    Game game=new Game();
+    game.choose(rand(3));
+    game.reveal();
+    if(swap)
+      game.change();
+    if(game.hasWon())
+      wins++;
+  }
+  String withWithout=swap?"with":"without";
+  double percent=(wins*100.0)/count;
+  print("playing $withWithout switching won $percent%");
+}
+
+test() {
+  for(int i=0;i<5;i++) {
+    Game g=new Game();
+    g.choose(i%3);
+    g.reveal();
+    print(g);
+    g.change();
+    print(g);
+    print("win==${g.hasWon()}");
+  }
+}
+
+main() {
+  play(10000,false);
+  play(10000,true);
+}