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Christmas Insanity!

2010 December 26
by Alec

Well, probably not the kind you’re expecting: Family drama, stress, gift anxiety, etc. No, I’m talking about “Insanity,” a game you probably haven’t heard of. It’s pretty simple. Ten holes on a piece of wood. Eight pegs; four red, four blue. Move all the pegs so that the colors are exactly switched. Pegs can only move in one direction. They can either move to an adjacent empty hole, or jump one peg of any color to an empty hole.

I picked it up and thought, gee, I could pretty quickly write a program to solve this. The game parameters were simple, yet it was a challenging enough problem that I couldn’t quickly pick it up and solve it. So I sat down with my laptop, fired up TextMate, and started hacking away. Python was the language of choice, mostly because I have a couple projects going on using it and needed the practice.Insanity

My algorithm is about as dumb as they get: Choose a peg at random, then randomly do a jump or “slide” move, if possible. I figured there weren’t that many possible moves, so it wouldn’t take that long. A few minutes of tweaking, and the program would keep getting stuck because of some poor initial moves. A little more tweaking (mostly increasing the number of tries per game) and it finally found a solution. Success!

See the code below. There’s undoubtedly substantial room for improvement, but it does the job, usually solving the problem after 5-10 minutes. I was pretty happy about the number of mistakes I didn’t make, after getting familiar with the python interpreter. A fun diversion on a snowy Christmas day.

insanity.py

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import random
 
def play_game():
    won = False
    while not won:
        game = Insanity()
        count = 0
        while count < 10000:
            if game.game_over():
                won = True
                print game.log
                print "You win!"
            game.move()
            count += 1
        if game.moves > 25:
            print game.log
 
class Insanity:
    def __init__(self):
        self.holes = []
        self.pegs = []
        self.log = ""
        self.moves = 0
        self.moved = False
        for i in range(10):
            h = Hole(i)
            if h.peg:
                self.pegs.append(h.peg)
            self.holes.append(h)
 
    def move(self):
        self.moved = False
        peg_to_move = self.pegs[int(random.random() * 8)]
        r = random.random()
        if r > 0.5:
            if self.can_jump(peg_to_move):
                self.jump(peg_to_move)
            elif self.can_slide(peg_to_move):
                self.slide(peg_to_move)
        else:
            if self.can_slide(peg_to_move):
                self.slide(peg_to_move)
            elif self.can_jump(peg_to_move):
                self.jump(peg_to_move)
        if self.moved:
            self.log += self.print_board()
 
    def jump(self, peg, distance=2):
        self.holes[peg.pos].peg = None
        new_pos = peg.pos + (distance * peg.direction())
        self.holes[new_pos].peg = peg
        peg.pos = new_pos
        self.moved = True
        self.moves += 1
 
    def slide(self, peg):
        self.jump(peg, 1)
 
    def can_jump(self,peg):
        return peg.can_jump() and not self.holes[peg.pos + peg.direction()].is_empty() and self.holes[peg.pos + (2 * peg.direction())].is_empty()
 
    def can_slide(self,peg):
        return not peg.at_end() and self.holes[peg.pos + peg.direction()].is_empty()
 
    def print_board(self):
        stri = ""
        for hole in self.holes:
            stri += hole.__str__()
        return stri + "\n"
 
    def game_over(self):
        for hole in self.holes[0:4]:
            if hole.is_empty() or not hole.peg.color == "red":
                return False
        for hole in self.holes[6:]:
            if hole.is_empty() or not hole.peg.color == "blue":
                return False
        return True
 
class Peg:
    def __init__(self, color, pos):
        self.color = color
        self.pos = pos
 
    def at_end(self):
        return (self.color == "blue" and self.pos == 9) or (self.color == "red" and self.pos == 0)
 
    def can_jump(self):
        return (self.color == "blue" and self.pos < 8) or (self.color == "red" and self.pos > 1)
 
    def direction(self):
        return 1 if self.color == "blue" else -1
 
    def p_color(self):
        return "B" if self.color == "blue" else "R"
 
    def __str__(self):
        return "P(%i%s)" % (self.pos, self.p_color(),)
 
class Hole:
    def __init__(self, i):
        self.num = i
        if i < 4:
            self.peg = Peg("blue", i)
        elif i > 5:
            self.peg = Peg("red", i)
        else:
            self.peg = None
 
    def is_empty(self):
        return self.peg == None
 
    def __str__(self):
        p = "E"
        if self.peg:
            p = self.peg.p_color()
        return "%i%s " % (self.num, p,)

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One Response
  1. Liju George permalink
    October 20, 2012

    Insane! 🙂

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