Created
October 18, 2013 10:03
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| import java.io.FileNotFoundException; | |
| import java.io.FileOutputStream; | |
| import java.io.PrintWriter; | |
| public class ThreeDoors { | |
| // Holds items | |
| private int cIndex;//Car index | |
| private int pIndex;//Guest choice | |
| private ThreeDoors() { | |
| PrintWriter outSw = null; | |
| PrintWriter outSt = null; | |
| try { | |
| outSw = new PrintWriter(new FileOutputStream("Switches.csv")); | |
| outSt = new PrintWriter(new FileOutputStream("Stays.csv")); | |
| } catch (FileNotFoundException e) { | |
| e.printStackTrace(); | |
| System.exit(0); | |
| } | |
| //CSV heads | |
| outSw.println("index, Prob: If guest always switches"); | |
| outSt.println("index, Prob: If guest always stays"); | |
| // Play style sum of results | |
| int swSum = 0, stSum = 0; | |
| double swProp = 0, stProp = 0; | |
| for (int i = 1; i <= 100000; i++) { | |
| // Play round | |
| play(); | |
| if (cIndex == pIndex) {//Wins on a stay | |
| stSum++; | |
| stProp = (double) stSum / i; | |
| } else {//Wins on switch | |
| swSum++; | |
| swProp = (double) swSum / i; | |
| } | |
| outSw.println(i +","+ swProp); | |
| outSt.println(i + "," + stProp); | |
| } | |
| outSw.close(); | |
| outSt.close(); | |
| } | |
| private void play() { | |
| // Car is put in 0-2 | |
| cIndex = randomDoor(); | |
| // Guest pick a door | |
| pIndex = randomDoor(); | |
| } | |
| public static void main(String[] args) { | |
| ThreeDoors td = new ThreeDoors(); | |
| System.out.print("Done"); | |
| } | |
| public static int randomDoor() { | |
| return (int) (Math.random() * 10 % 3); | |
| } | |
| } |
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This is a real plain example of the Monty Hall problem.