Montyhall

montyhall.pl

#!/usr/bin/perl -w

use strict;
use warnings;

sub automatic_choice {
  my ($n, $i, $j, $c, $u, $d, $t);
  my ($win, $guess, $switch);
  
  print STDERR "How many doors? [ > 1 ]: ";
  $n = int(<STDIN>);
  
  print STDERR "How many iterations? [ > 1 ]: ";
  $j = int(<STDIN>);
  
  print "user#\tcar#\tswitch?\twin?\n";
  for ($i = 0; $i < $j; $i++) {
    $c = int(rand($n)) + 1;
    $u = int(rand($n)) + 1;
    $d = $c;
    if ($u == $c) {
      $guess++;
      while ($d == $c) {
        $d = int(rand($n)) + 1;
      }
    }
    $t = 1; # (rand() >= .5) ? 1 : 0;
    if ($t > 0) {
      $switch++;
      $u = $d;
    }
    print "$u\t$c\t$t\t";
    if ($u == $c) {
      $win++;
      print "1";
    } else {
      print "0";
    }
    print "\n";
  }
  print "Total:\tWin\tLoss\tSwitches\n" .
    "\t$win\t" . ($j - $win) . "\t$switch\n";
}

sub manual_choice {
  
  my ($n, $c, $u, $d, $t);
  
  $n = 100;
  $c = int(rand($n)) + 1;
  
  print "There are $n doors, and a car behind one of them.\n" . 
    "Which door to pick? [1..$n]: ";
  $u = int(<STDIN>);
  
  # If user selected car..
  if ($u == $c) {
    # .. then pick some other door to keep.
    while ($d == $c) { $d = int(rand($n)) + 1; }
  } else {
    # .. else pick the car.
    $d = $c;
  }
  
  print "Car is behind the remaining door or your choice, door $u. Change? [y,n]: ";
  $t = <STDIN>;
  if ($t =~ /[yY].*/) {
    print "You switched to door $d.\n";
    $u = $d;
  }
  
  if ($u == $c) {
    print "You won a car.\n";
  } else {
    print "You got nothing. NOTHING.\n";
  }
  
}

sub main {
  #manual_choice();
  automatic_choice();
}

main();