Programming implementation of Monty Hall Problem.

MontyHallProblem.js

/*
 * Programming implementation of Monty Hall Problem.
 * By Prof.X (http://weibo.com/xavieryao)
 */

//Variants to store experiment time and result.
var time = 0.0;
var changeAndWin = 0.0;
var winWithoutChange = 0.0;


while(true){
	/*
	 * There are three doors, Door 0,1,2.
 	*/
	var doors = new Array();


	/*
	 * Behind one of them there hides an award.
	 */
	var doorWithAward = parseInt(3*Math.random());
	doors[doorWithAward] = 'Award';
	var emptyDoors;
	switch(doorWithAward){
		case 0:
		emptyDoors = [1,2];
		break;
		case 1:
		emptyDoors = [0,2];
		break;
		case 2:
		emptyDoors = [0,1];
	}

	/*
	 * Pick one of the doors.
	 */
	var pickedDoor = parseInt(3*Math.random());

	 /*
	  * Open an empty door.
	  */
	var openedDoor;
	if(pickedDoor == doorWithAward){
		openedDoor = emptyDoors[parseInt(2*Math.random())];
	}else{
		openedDoor = 3 - doorWithAward - pickedDoor;
	}

	/*
	 * Change selection.
	 */

	 var changed = false;
	 if(Math.random()<0.5){
	 	pickedDoor = 3 - openedDoor - pickedDoor;
	 	changed = true;
	 }

	 /*
	  * Open the door.
	  */
	if(doors[pickedDoor]=='Award'){
		if(changed){
	    	changeAndWin ++;
		}else{
			winWithoutChange ++;
		}
	}

	 time++;
	 console.log('第'+time+'次实验，更换门且获胜的频率为:'+changeAndWin/time+'  未更换获胜的频率为:'+winWithoutChange/time+ ' 更换后获胜的频率是更换前的'+changeAndWin/winWithoutChange+'倍');
}