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) + '%'
+	};
+}

Task/Monty-Hall-problem/JavaScript/monty-hall-problem-2.js

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+montyhall(1000, 3)
+Object {stayWins: "349 34.9%", switchWins: "651 65.1%"}
+montyhall(1000, 4)
+Object {stayWins: "253 25.3%", switchWins: "384 38.4%"}
+montyhall(1000, 5)
+Object {stayWins: "202 20.2%", switchWins: "265 26.5%"}

Task/Monty-Hall-problem/JavaScript/monty-hall-problem-3.js

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+var totalGames = 10000,
+    selectDoor = function () {
+	return Math.floor(Math.random() * 3); // Choose a number from 0, 1 and 2.
+    },
+    games = (function () {
+	var i = 0, games = [];
+
+	for (; i < totalGames; ++i) {
+	    games.push(selectDoor()); // Pick a door which will hide the prize.
+	}
+
+	return games;
+    }()),
+    play = function (switchDoor) {
+	var i = 0, j = games.length, winningDoor, randomGuess, totalTimesWon = 0;
+
+	for (; i < j; ++i) {
+	    winningDoor = games[i];
+	    randomGuess = selectDoor();
+	    if ((randomGuess === winningDoor && !switchDoor) ||
+		(randomGuess !== winningDoor && switchDoor))
+	    {
+		/*
+		 * If I initially guessed the winning door and didn't switch,
+		 * or if I initially guessed a losing door but then switched,
+		 * I've won.
+		 *
+		 * The only time I lose is when I initially guess the winning door
+		 * and then switch.
+		 */
+
+		totalTimesWon++;
+	    }
+	}
+	return totalTimesWon;
+    };
+
+/*
+ * Start the simulation
+ */
+
+console.log("Playing " + totalGames + " games");
+console.log("Wins when not switching door", play(false));
+console.log("Wins when switching door", play(true));

Task/Monty-Hall-problem/JavaScript/monty-hall-problem-4.js

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+Playing 10000 games
+Wins when not switching door 3326
+Wins when switching door 6630