A-M baby

Task/Monty-Hall-problem/JavaScript/monty-hall-problem-1.js

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+function montyhall(tests, doors) {
+	'use strict';
+	tests = tests ? tests : 1000;
+	doors = doors ? doors : 3;
+	var prizeDoor, chosenDoor, shownDoor, switchDoor, chosenWins = 0, switchWins = 0;
+	
+	// randomly pick a door excluding input doors
+	function pick(excludeA, excludeB) {
+		var door;
+		do {
+			door = Math.floor(Math.random() * doors);
+		} while (door === excludeA || door === excludeB);
+		return door;
+	}
+	
+	// run tests
+	for (var i = 0; i < tests; i ++) {
+		
+		// pick set of doors
+		prizeDoor = pick();
+		chosenDoor = pick();
+		shownDoor = pick(prizeDoor, chosenDoor);
+		switchDoor = pick(chosenDoor, shownDoor);
+
+		// test set for both choices
+		if (chosenDoor === prizeDoor) {
+			chosenWins ++;
+		} else if (switchDoor === prizeDoor) {
+			switchWins ++;
+		}
+	}
+	
+	// results
+	return {
+		stayWins: chosenWins + ' ' + (100 * chosenWins / tests) + '%',
+		switchWins: switchWins + ' ' + (100 * switchWins / tests) + '%'
+	};
+}