Ruby on Rails (or Trackety Track)

48

9

You are Ruby, a railway engineer. Your task is to lay track in any given valley such that it visits every station (M). The amount of track laid is not important, but it must be laid in one continuous path which starts and ends at the valley entrance/exit point (>) and does not, at any point cross itself. There are a few other constraints: mountains(^) are impassable so you must go around them, rivers(~) must be crossed using a bridge(X), and the edge of the valley (#) is also impassable.

The Rules of the Track

If track is not laid properly there will be derailments and nobody wants that, so here are the rules over track placement.

There are four kinds of track: - | / \.
Here's how each one may be combined with the others:

Allowed combinations from - (in the centre of each example):

#####  #####  #####  #####  #####  #####  #####
#   #  #   #  #\  #  #   #  #  /#  #\ /#  #   #
#---#  # --#  # --#  #-- #  #-- #  # - #  # - #
#   #  #/  #  #   #  #  \#  #   #  #   #  #/ \#
#####  #####  #####  #####  #####  #####  #####

- may never be combined with |. This is too sharp a turn for the trains to make safely.

Allowed combinations from / (in the centre of each example):

#####  #####  #####  #####  #####  #####  #####
#  /#  #  -#  #  |#  #  /#  #  /#  #  -#  #  |#
# / #  # / #  # / #  # / #  # / #  # / #  # / #
#/  #  #/  #  #/  #  #|  #  #-  #  #|  #  #-  #
#####  #####  #####  #####  #####  #####  #####

\ may never be combined with /. This is too sharp a turn for the trains to make safely.

Allowed combinations from \ (in the centre of each example):

#####  #####  #####  #####  #####  #####  #####
#\  #  #-  #  #|  #  #\  #  #\  #  #-  #  #|  #
# \ #  # \ #  # \ #  # \ #  # \ #  # \ #  # \ #
#  \#  #  \#  #  \#  #  |#  #  -#  #  |#  #  -#
#####  #####  #####  #####  #####  #####  #####

Allowed combinations from | (in the centre of each example):

#####  #####  #####  #####  #####  #####  #####
# | #  #\  #  #  /#  # | #  # | #  #  /#  #\  #
# | #  # | #  # | #  # | #  # | #  # | #  # | #
# | #  # | #  # | #  #/  #  #  \#  #  \#  #/  #
#####  #####  #####  #####  #####  #####  #####

Tracks may combine with the stations, bridges and valley entrance/exit in the following ways:

#####  #####  #####
#\|/#  #\|/#  #/  #
#-M-#  #-X-#  >-  #
#/|\#  #/|\#  #\  #
#####  #####  #####

Stations have turn-tables, so it's permissible to leave a station at a sharp angle (though not back the way you came - you wouldn't want to crash into the next scheduled train coming the other way!).
Bridges are for crossing rivers so you must exit the bridge on the opposite side of the river that you entered it.

Input

Input will be via STDIN for programs or a function argument for functions. If your function needs a name in order for me to run it on my input then that name declaration should be included in the byte count.

The input will be a single string with line-breaks. Each line within your input will always be the same length as the others, giving you a rectangular input. The edge of the input will always be solid and impassable (#) except for the point of entry. Any given input will have at least one valid answer.

Output

Your output should be returned as a single string with line-breaks from a function, or printed/echoed to the screen for full programs.

The output should be the same as the input but with the track characters added.

Scoring

Winner will be the shortest code in bytes.

Test cases

###########
#    M    #
#   ^     #
>  ^^  M  #
#    ^    #
#~~~~~~~~~#
# M       #
#     ^^  #
#        M#
###########


#################
#               #
#   M         M #
#       ^       #
#        ^ M    #
#~~~~~~~^       #
#               #
#   ^           #
#   M^          #
#    ^          #
> ^^^          M#
#               #
#        M      #
#################

###############
# M   ~       #
#     ~       #
>     ~    M  #
#     ~       #
#     ~       #
#     ~       #
###############

Possible solutions to test cases

###########
# ---M    #
#/  ^ \   #
>  ^^  M  #
#\   ^ |  #
#~X~~~~X~~#
# M     \ #
#  \  ^^ |#
#   -----M#
###########

#################
#               #
#   M---------M #
#   |   ^    /  #
#  /     ^ M-   #
#~X~~~~~^  |    #
# |         \   #
#  \^        \  #
# --M^        \ #
#/   ^         |#
> ^^^          M#
#\            / #
# -------M----  #
#################

###############
# M   ~       #
#/ \  ~       #
>   --X----M  #
#\    ~    |  #
# \   ~   /   #
#  ---X---    #
###############

Gareth

Posted 2016-12-28T22:01:03.940

Reputation: 11 678

8Finally! This challenge has been in the Sandbox forever! – mbomb007 – 2016-12-28T23:02:35.017

18@mbomb007 Not quite, there were 4 months between this site starting and the question being posted in the sandbox ;-) – Gareth – 2016-12-28T23:03:51.193

I can't wait to see someone solve this one using Ruby on Rails – Daniel – 2016-12-29T17:29:45.240

Are rivers always horizontal only? – briantist – 2016-12-29T21:54:27.473

@briantist No. They are in both the examples, but they could be in any direction. – Gareth – 2016-12-29T22:24:56.567

1@Gareth can they have turns? Can they be wider than one cell? – Martin Ender – 2016-12-30T14:08:51.827

@MartinEnder Turns - yes. Wider than 1 cell - no. – Gareth – 2016-12-30T15:16:41.277

Oh boy. Are there any time/memory constraints; Can we just brute-force it? – SIGSTACKFAULT – 2017-01-05T17:47:06.477

@Blacksilver No strict constraints, but if I can't run it to completion on the two test inputs I won't be able to upvote or accept the answer. – Gareth – 2017-01-05T22:19:05.000

I just realized brute-force is a terrible idea since the possible solutions is n^4 for a valley with n spaces. Maybe if I limit it to possible connections from there... n^3ish, not as bad – SIGSTACKFAULT – 2017-01-05T22:52:06.347

To clear up the confuzzlement, I've added another test case to show vertical rivers. – SIGSTACKFAULT – 2017-01-05T23:06:26.890

1wait - What if we need to move just one space vertically while going horizontally? – SIGSTACKFAULT – 2017-01-05T23:11:02.460

@Blacksilver Yes, I had to change my test inputs after updating the question in the sandbox for that reason. Assume that any given input will have at least one valid answer. – Gareth – 2017-01-06T18:29:55.283

@LliwTelracs I think I see what you mean - the crossing on the right in my test solution is too close to the valley edge. I'll alter that test case now. – Gareth – 2017-03-01T14:14:31.590

@LliwTelracs I don't see the mistake in the second test solution though? – Gareth – 2017-03-01T14:17:45.320

@LliwTelracs No, they don't have to be. – Gareth – 2017-03-01T16:31:00.607

Would I be correct in saying that you can only turn up to 45 degrees when going across a bridge? Or are you able to turn up to 90 degrees? – fəˈnɛtɪk – 2017-03-01T17:05:20.150

@LliwTelracs You can turn up to 90 degrees when crossing a bridge. – Gareth – 2017-03-01T19:54:02.510

So do bridges act like normal rails except that you can only exit in a straight line from them? It might help if you gave all the individual examples for a bridge with a diagonal entry and a bridge with a vertical entry. – fəˈnɛtɪk – 2017-03-01T20:11:17.337

@LliwTelracs The only rule with a bridge is that you must exit on the opposite side of the river. – Gareth – 2017-03-01T20:15:04.860

If the rivers can end at any given point, what is the opposite side of the river at the end of a river. – fəˈnɛtɪk – 2017-03-01T20:16:49.367

@LliwTelracs Okay, I see what you're getting at. At the end of a river imagine that the line formed by the last two river characters stretches off into infinity. You need to exit the bridge on the opposite side of that imaginary line. – Gareth – 2017-03-01T20:23:30.913

Can rivers fork? – fəˈnɛtɪk – 2017-03-03T21:06:43.590

@LliwTelracs For this question, no. – Gareth – 2017-03-03T21:15:18.527

1My head hurts. I have been working on this and it is so hard – Christopher – 2017-03-29T15:46:41.827

@DownChristopher I can help - but would you share the bounty if you do so? – Matthew Roh – 2017-03-31T12:28:22.073

Forget shortest code -- Let's just get something that WORKS first...... this is like the next GoL Tetris challenge... – HyperNeutrino – 2017-03-31T12:29:05.780

Can you place bridges over land? (Question about Abusing Rules) – HyperNeutrino – 2017-03-31T12:30:15.933

1@HyperNeutrino More like: the WAY AHEAD OF TIME GoL Tetris challenge. – Matthew Roh – 2017-03-31T12:30:20.283

1@HyperNeutrino No, you can only use bridges over rivers. – Gareth – 2017-03-31T12:30:47.520

@SIGSEGV Good point. This was sandboxed really early, right? – HyperNeutrino – 2017-03-31T12:31:15.523

@HyperNeutrino Correct. – Matthew Roh – 2017-03-31T12:31:36.860

Valley entrances hurts my head badly :( – Matthew Roh – 2017-03-31T12:32:18.573

1..I just want to put T(Teleporter) around the stations to teleport the train from one station to another – Matthew Roh – 2017-03-31T12:34:03.603

Can input be taken "like this"? – HyperNeutrino – 2017-03-31T12:39:32.040

@HyperNeutrino I'm not sure what you mean. Are you asking if the input can be embeded in the code? If so, then no. It would need to be from STDIN or from a function argument (though there's nothing to stop you doing embedding it whilst you are developing an answer). – Gareth – 2017-03-31T12:42:13.873

@HyperNeutrino Just asking- Did you just attempt to put bridges literally everywhere – Matthew Roh – 2017-03-31T12:42:35.553

@SIGSEGV Maybe... Well I mean I didn't make code to do that because I knew OP wouldn't allow it :P – HyperNeutrino – 2017-03-31T12:43:27.207

@Gareth I'm wondering if I can take input with quotes around it (the single string) – HyperNeutrino – 2017-03-31T12:43:48.207

1@HyperNeutrino If you want to add quotes around the string I have no objection to that. – Gareth – 2017-03-31T12:45:29.827

Introducing bogorail – Matthew Roh – 2017-03-31T12:54:31.963

@SIGSEGV for sure. If we get it working I made a chat here it ended up on sci-fi SE as that is my main.

– Christopher – 2017-03-31T15:10:28.040

Answers

26

Python 2, 3990 3430 4412 4313 bytes

This is a basically an A* with a ugly heuristic and an ugly getChildren method. To run the 3 test cases consecutively takes 6.5s on my machine. The function f is the solution here. It takes the map as a string and returns the solved map as a string.

from itertools import*
import sys
from Queue import*
A,B,C,D,E,F,G=">|\\/-MX";H=range;I=permutations;J=set;K=abs;L=len
class M:
	@staticmethod
	def T(a):return a in">|\\/-MX"
	@staticmethod
	def C(a,b,c,d,x,y,e):
		if not M.T(d)or not M.T(e):return 0
		if e in"MX"and d in"MX"and e!=d:return 1
		if d==A:return x>0 and(e==D and y==-1 or e==E and y==0 or e==C and y==1)
		if d==F:return e==C and K(x+y)==2 or e==D and x+y==0 or e==B and x==0 or e==E and y==0
		if d==G:
			if b!=0!=c and K(b-x)+K(c-y)==1:return 0
			return e==C and K(x+y)==2 or e==D and x+y==0 or e==B and x==0 or e==E and y==0
		if e!=""and e in"MX>"and a!=""and a in"MX>":return M.C("",0,0,a,-b,-c,d)and M.C("",0,0,e,-x,-y,d)
		elif e!=""and e in"MX>"and a!="":return M.C("",0,0,d,b,c,a)and M.C("",0,0,e,-x,-y,d)
		elif e!=""and e in"MX>"and a=="":return M.C("",0,0,e,-x,-y,d)
		elif a!=""and a in"MX>":return M.C("",0,0,a,-b,-c,d)and M.C("",0,0,d,x,y,e)
		f=[[E,-1,0,E,1,0,E],[D,-1,1,E,1,0,E],[C,-1,-1,E,1,0,E],[E,-1,0,E,1,1,C],[E,-1,0,E,1,-1,D],[C,-1,-1,E,1,-1,D],[D,-1,1,E,1,1,C],[D,-1,1,D,1,-1,D],[D,-1,1,D,1,-1,E],[D,-1,1,D,1,-1,B],[B,-1,1,D,1,-1,D],[E,-1,1,D,1,-1,D],[B,-1,1,D,1,-1,E],[E,-1,1,D,1,-1,B],[C,-1,-1,C,1,1,C],[C,-1,-1,C,1,1,E],[C,-1,-1,C,1,1,B],[B,-1,-1,C,1,1,C],[E,-1,-1,C,1,1,C],[B,-1,-1,C,1,1,E],[E,-1,-1,C,1,1,B],[B,0,-1,B,0,1,B],[C,-1,-1,B,0,1,B],[D,1,-1,B,0,1,B],[B,0,-1,B,-1,1,D],[B,0,-1,B,1,1,C],[D,1,-1,B,1,1,C],[C,-1,-1,B,-1,1,D]];g=0;h=[a,b,c,d,x,y,e];j=[0,3][a==""]
		for k in f:
			l=1;m=1;n=[k[6],k[4],k[5],k[3],k[1],k[2],k[0]]
			for i in H(j,L(k)):
				if k[i]!=h[i]:l=0
				if n[i]!=h[i]:m=0
			if l or m:g=1
		return g
	def __init__(s,a):s.m=[list(x)for x in a.split("\n")]
	def __str__(s):return"\n".join(["".join(x)for x in s.m])
	def A(s):return str(s)
	def B(s):return L(s.m[0])
	def D(s):return L(s.m)
	def E(s):
		a=[]
		for y in H(1,s.D()-1):
			for x in H(1,s.B()-1):
				if s.J(x,y)==F and L(s.H(x,y, F))==0:a+=[(x,y)]
		return a
	def F(s):
		for y in H(s.D()):
			for x in H(s.B()):
				if s.J(x,y)==A:return(x,y)
	def G(s):
		a=0
		for y in H(0,s.D()-1):
			for x in H(0,s.B()-1):
				b=s.J(x,y)
				c=L(s.H(x,y,b))
				if b==A:
					if c==0:a=(x,y)
					c=0
				if c==1:return(x,y)
		if a!=0:
			return a
		raise ValueError()
	def J(s,x,y):return s.m[y][x]
	def K(s,x,y,b):
		a=[[i for i in row]for row in s.m];a[y][x]=b
		return"\n".join("".join(x)for x in a)
	def H(s,x,y,c):
		d=[];e=[]
		for a,b in J(I([-1,-1,0,1,1],2)):
			g=s.J(x+a,y+b)
			if M.T(g)and M.C("",0,0,c,a,b,g):e+=[[g,a,b]]
		if L(e)==1:return[e[0][0]]
		if L(e)==0:return[]
		for g,h in I(e,2):
			i,j,k=g;l,m,n=h;o=x + m;p=y + n
			if M.C(i,j,k,c,m,n,l):
				if l==F:
					if L(s.H(o,p,l))>=1:d+=[l]
				else:d+=[l]
		return d
	def I(s,x,y,a,b):
		if a==0 or b==0:return 0
		a=s.J(x+a,y);b=s.J(x,y+b)
		return(M.T(a)or a==F)and(M.T(b)or b==F)
class P:
	@staticmethod
	def A(x0,y0,x1,y1):return K(x0-x1)+4*K(y0-y1)
	def __init__(s,a,p,t=0,g=0):
		s.a=[];s.b=p;s.c=a;s.d=[a];s.e=t;s.f=g
		if p:s.d=p.d[:];s.d+=[a];s.e=p.e;s.f=p.f
		s.g=M(a);s.h=s.B()
	def __str__(s):return s.g.A()
	def B(s):
		a=0;b=1;c=0
		try:c=s.g.G()
		except:a=1
		d=s.g.E();e=s.g.F();g=[]
		if L(d)==0 and not a:g=P.A(c[0],c[1],e[0],e[1])+b
		elif L(d)==0 and a:return 0
		elif c:
			h,i=c
			for j in combinations(d,L(d)):
				k=0
				for x,y in j:k+=P.A(h,i,x,y);h,i=x,y
				g+=[k]
			g=min(g);g+=s.g.B()+s.g.D()+b
		else:return sys.maxint
		if g<1:return 0
		return g
	def C(s):
		try:a=s.g.G()
		except:s.a=[];return
		b=s.g.J(a[0],a[1]);c=("",0,0);e=(0,0)
		for x,y in J(I([-1,-1,0,1,1],2)):
			g,h=a[0]+x,a[1]+y;i=s.g.J(g,h)
			if M.T(i)and M.C("",0,0,i,x,y,b):c=(i,x,y)
			if i=="~":e=(x,y)
		for x,y in J(I([-1,-1,0,1,1],2)):
			g,h=a[0]+x,a[1]+y;i=s.g.J(g,h)
			if not(i in"^#"or M.T(i)):
				for j in"-|\\/":
					if i=="~":
						j=G 
						if c[0]==G:continue
					if c[0]==G and K(e[0])==1 and y==c[1]:continue
					if c[0]==G and K(e[1])==1 and x==c[0]:continue
					k=s.g.H(g,h,j);l=L(k)
					if(l==1 or l==2 and A in k)and M.C(c[0],c[1],c[2],b,x,y,j)and not s.g.I(a[0],a[1],x,y):
						try:s.a+=[P(s.g.K(g,h,j),s)]
						except:pass
def f(x):
	d=[];a=[];b=PriorityQueue();b.put((0,P(x,0)))
	while not d and b.qsize():
		c=b.get()[1];c.C();a+=[c.c]
		for e in c.a:
			if e.c not in a:
				if not e.h:d=e.d
				b.put((e.h,e))
	return d[-1]

Try it online!

Test Cases

Test 1

enter image description here

###########
# ---M    #
#/  ^ \   #
>  ^^  M  #
#\   ^ |  #
#~X~~~~X~~#
# M    |  #
#  \  ^^\ #
#   -----M#
###########

Test 2

enter image description here

#################
#               #
#   M---------M #
#  /    ^    /  #
# |      ^ M-   #
#~X~~~~~^   \   #
# |          |  #
#  \^        |  #
# --M^       |  #
#/   ^-       \ #
> ^^^/ \       M#
#\  /   \     / #
# --     M----  #
#################

Test 3

enter image description here

###############
# M   ~       #
#/ \  ~       #
>   --X----M  #
#\    ~   /   #
# ----X---    #
#     ~       #
###############

Source Code

A* State + A* Solver Class

I actually golfed these out of my solution. But they exist in my 'readable' version. The State class is generic and meant to be implemented. The Solver class takes a start state and then follows that states heuristic getDist.

from Queue import PriorityQueue

# A* State
class State(object):
    # The type of value should be a primative
    def __init__(self, value, parent, start=0, goal=0):
        self.children = []
        self.parent = parent
        self.value = value
        self.dist = 0
        if parent:
            self.path = parent.path[:]
            self.path.append(value)
            self.start = parent.start
            self.goal = parent.goal
        else:
            self.path = [value]
            self.start = start
            self.goal = goal

    # Implement a heuristic for calculating the distance from this state to the goal
    def getDist(self):
        pass

    # Implement a way to create children for this state
    def createChildren(self):
        pass

# A* Solver 
# Note: if maxmin = 1: Solver tries to minimize the distance
#       if maxmin = -1: Solver tries to maximize the distance
class AStar_Solver:
    def __init__(self,startState,maxmin=1):
        self.path = []
        self.visitedQueue = []
        self.priorityQueue = PriorityQueue()
        self.priorityQueue.put((0,startState))
        self.startState = startState
        self.maxmin = maxmin
        self.count = 0

    # Create a png of the string 'qPop'
    def imager(self,qPop):
        # Imager(qPop,str(self.count).rjust(5,"0")+".png")
        # print str(qPop)+"\n"
        self.count += 1

    # Solve the puzzle
    def solve(self):
        while(not self.path and self.priorityQueue.qsize()):
            closestChild = self.priorityQueue.get()[1]
            self.imager(str(closestChild))
            closestChild.createChildren()
            self.visitedQueue.append(closestChild.value)
            for child in closestChild.children:
                if child.value not in self.visitedQueue:
                    if not child.dist:
                        self.imager(str(child))
                        self.path = child.path
                        break
                    self.priorityQueue.put((self.maxmin*child.dist,child))
        if not self.path:
            print "Goal was not reachable"
        return self.path

State Class

This is the implementation of the A* state class. The most important method here is getDist, it is the heuristic for determining how close self is to the goal. It is basically the minimum distance to visit all the remaining destinations and get back to start.

from A_Star import State,AStar_Solver
from Ruby_Map import Map
from itertools import combinations, permutations
import sys

# A state class designed to work with A*
class State_Pathfinder(State):

    # This is deprecated
    @staticmethod
    def toValue(location):
        return str(location[0])+","+str(location[1])

    # Calculate the weighted distance between 2 points.
    # Not sure why the deltaY is more weighted. My theory
    # is that it is because the starting point is always
    # on a side. So vertical space is most precious?
    @staticmethod
    def distance(x0,y0,x1,y1):
        # return (abs(x0-x1)**2+abs(y0-y1)**2)**.5
        return 1*abs(x0-x1)+4*abs(y0-y1)

    def __init__(self, maps, parent, value=0, start=0, goal=0):
        super(State_Pathfinder,self).__init__(maps,parent,start,goal)
        self.map = Map(maps)
        self.dist = self.getDist()
        if not value:
            location = self.map.getLocation()
            self.value = maps
            self.path = [self.value]

    def __str__(self):
        return self.map.getDisplay()

    # The heuristic function that tells us
    # how far we are from the goal
    def getDist(self):
        blownup = False
        WEIGHT = 1
        location = None
        try:
            location = self.map.getLocation()
        except ValueError as e:
            blownup = True
        destinations = self.map.getDestinations()
        goal = self.map.getGoal()
        dist = []
        if len(destinations) == 0 and not blownup:
            dist = State_Pathfinder.distance(location[0],location[1],goal[0],goal[1])+WEIGHT
        elif len(destinations) == 0 and blownup:
            return 0
        elif location:
            oldX,oldY = location
            for path in combinations(destinations,len(destinations)):
                length = 0
                for pair in path:
                    x,y = pair
                    length += State_Pathfinder.distance(oldX,oldY,x,y)
                    oldX,oldY = x,y
                dist.append(length)
            dist = min(dist)
            dist += self.map.getWidth()+self.map.getHeight()+WEIGHT
        else:
            return sys.maxint
        if dist<1:
            return 0
        return dist

    # Creates all possible (legal) child states of this state
    def createChildren(self):
        if not self.children:
            try:
                location = self.map.getLocation()
            except:
                self.children = []
                return
            track = self.map.get(location[0],location[1])
            intrack = ("",0,0)
            river = (0,0)
            for x,y in set(permutations([-1,-1,0,1,1],2)):
                realX,realY = location[0]+x,location[1]+y
                adjacent = self.map.get(realX,realY)
                if Map.isTrack(adjacent) and Map.isConnected("",0,0,adjacent,x,y,track):
                    intrack = (adjacent,x,y)
                if adjacent=="~":
                    river = (x,y)
            for x,y in set(permutations([-1,-1,0,1,1],2)):
                realX,realY = location[0]+x,location[1]+y
                adjacent = self.map.get(realX,realY)
                if not Map.isBlocking(adjacent) and not adjacent in "M":
                    for outtrack in "-|\\/":
                        if adjacent=="~":
                            outtrack="X"
                            if intrack[0]=="X":continue
                        if intrack[0]=="X" and abs(river[0])==1 and y==intrack[1]:continue
                        if intrack[0]=="X" and abs(river[1])==1 and x==intrack[0]:continue
                        connections = self.map.getConnections(realX,realY,outtrack)
                        hoppin = len(connections)
                        connected = Map.isConnected(intrack[0],intrack[1],intrack[2],track,x,y,outtrack)
                        blocked = self.map.isBlocked(location[0],location[1],x,y)
                        if (hoppin==1 or hoppin==2 and ">" in connections) and connected and not blocked:
                            try:
                                maps = self.map.set(realX,realY,outtrack)
                                value = State_Pathfinder.toValue((realX,realY))
                                child = State_Pathfinder(maps,self,value)
                                self.children.append(child)
                            except ValueError as e:
                                print "Bad kid"
                                print e

# The solution function. Takes a map string
# and returns a map string.
def f(mapX):
    a = AStar_Solver(State_Pathfinder(mapX,0))
    a.solve()
    print a.path[-1]

if __name__ == "__main__":

    map1 = """###########
#    M    #
#   ^     #
>  ^^  M  #
#    ^    #
#~~~~~~~~~#
# M       #
#     ^^  #
#        M#
###########"""


    map2 = """#################
#               #
#   M         M #
#       ^       #
#        ^ M    #
#~~~~~~~^       #
#               #
#   ^           #
#   M^          #
#    ^          #
> ^^^          M#
#               #
#        M      #
#################"""

    map3 = """###############
# M   ~       #
#     ~       #
>     ~    M  #
#     ~       #
#     ~       #
#     ~       #
###############"""

    f(map3)
    f(map2)
    f(map1)

Map Class

This class stores and processes the map. The isConnected method is probably the most important piece. It tests to see if 2 pieces of track are connected.

from itertools import permutations,combinations

# A map class designed to hold string map
# the specification is found here:
# http://codegolf.stackexchange.com/questions/104965/ruby-on-rails-or-trackety-track
class Map(object):

    # Is 'track' part of the railroad?
    @staticmethod
    def isTrack(track):
        return track in ">|\\/-MX"

    # Can I not build on this terrian?
    @staticmethod
    def isBlocking(terrian):
        return terrian in "^#" or (Map.isTrack(terrian) and not terrian=="M")

    # Are these 3 consecuative tracks connected in a legal fashion?
    @staticmethod
    def isConnected(inTerrian,relativeXin,relativeYin,centerTerrian,relativeXout,relativeYout,outTerrian):
        tin = inTerrian
        xin = relativeXin
        yin = relativeYin
        x = relativeXout
        y = relativeYout
        tout = outTerrian
        center = centerTerrian

        if not Map.isTrack(center) or not Map.isTrack(tout):
            return False

        if tout in "MX" and center in "MX" and tout!=center:
            return True



        if center == ">":
            return x>0 and (\
                tout == "/" and y == -1 or \
                tout == "-" and y == 0 or \
                tout == "\\" and y == 1 \
                )

        if center == "M":
            return tout == "\\" and abs(x+y) == 2 or \
                tout == "/" and x+y == 0 or \
                tout == "|" and x == 0 or \
                tout == "-" and y == 0

        if center == "X":
            if xin!=0!=yin and abs(xin-x)+abs(yin-y) == 1:
                return False
            return tout == "\\" and abs(x+y) == 2 or \
                tout == "/" and x+y == 0 or \
                tout == "|" and x == 0 or \
                tout == "-" and y == 0

        if tout!="" and tout in "MX>" and tin!="" and tin in "MX>":
            return Map.isConnected("",0,0,tin,-xin,-yin,center) and Map.isConnected("",0,0,tout,-x,-y,center)
        elif tout!="" and tout in "MX>" and tin!="":
            return Map.isConnected("",0,0,center,xin,yin,tin) and Map.isConnected("",0,0,tout,-x,-y,center)
        elif tout!="" and tout in "MX>" and tin=="":
            return Map.isConnected("",0,0,tout,-x,-y,center)
        elif tin!="" and tin in "MX>":
            return Map.isConnected("",0,0,tin,-xin,-yin,center) and Map.isConnected("",0,0,center,x,y,tout)

        allowed = [ \
            ["-",-1,0,"-",1,0,"-"], \
            ["/",-1,1,"-",1,0,"-"], \
            ["\\",-1,-1,"-",1,0,"-"], \
            ["-",-1,0,"-",1,1,"\\"], \
            ["-",-1,0,"-",1,-1,"/"], \
            ["\\",-1,-1,"-",1,-1,"/"], \
            ["/",-1,1,"-",1,1,"\\"], \

            ["/",-1,1,"/",1,-1,"/"], \
            ["/",-1,1,"/",1,-1,"-"], \
            ["/",-1,1,"/",1,-1,"|"], \
            ["|",-1,1,"/",1,-1,"/"], \
            ["-",-1,1,"/",1,-1,"/"], \
            ["|",-1,1,"/",1,-1,"-"], \
            ["-",-1,1,"/",1,-1,"|"], \

            ["\\",-1,-1,"\\",1,1,"\\"], \
            ["\\",-1,-1,"\\",1,1,"-"], \
            ["\\",-1,-1,"\\",1,1,"|"], \
            ["|",-1,-1,"\\",1,1,"\\"], \
            ["-",-1,-1,"\\",1,1,"\\"], \
            ["|",-1,-1,"\\",1,1,"-"], \
            ["-",-1,-1,"\\",1,1,"|"], \

            ["|",0,-1,"|",0,1,"|"], \
            ["\\",-1,-1,"|",0,1,"|"], \
            ["/",1,-1,"|",0,1,"|"], \
            ["|",0,-1,"|",-1,1,"/"], \
            ["|",0,-1,"|",1,1,"\\"], \
            ["/",1,-1,"|",1,1,"\\"], \
            ["\\",-1,-1,"|",-1,1,"/"] \
        ]

        passing = False
        forward = [tin,xin,yin,center,x,y,tout]
        start = [0,3][tin==""]

        for allow in allowed:
            maybeF = True
            maybeB = True
            backallowed = [allow[6],allow[4],allow[5],allow[3],allow[1],allow[2],allow[0]]
            for i in range(start,len(allow)):
                if allow[i]!=forward[i] and str(forward[i])not in"*":
                    maybeF = False
                if backallowed[i]!=forward[i] and str(forward[i])not in"*":
                    maybeB = False
            if maybeF or maybeB:
                passing = True
        return passing

    def __init__(self,mapString):
        self.indexableMap = [list(x) for x in mapString.split("\n")]

    def __str__(self):
         return "\n".join(["".join(x) for x in self.indexableMap])

    # Get the string representation of this map
    def getDisplay(self):
        return self.__str__()

    # Get map width
    def getWidth(self):
        return len(self.indexableMap[0])

    # Get map height
    def getHeight(self):
        return len(self.indexableMap)

    # Get unvisited destinations
    def getDestinations(self):
        destinations = []
        for y in xrange(1,self.getHeight()-1):
            for x in xrange(1,self.getWidth()-1):
                sigma = 2
                if self.get(x,y)=="M":
                    sigma = len(self.getConnections(x,y,"M"))
                    if sigma==0:
                        destinations.append((x,y))
        return destinations

    # Get the x,y of the goal (endpoint)
    def getGoal(self):
        for y in xrange(self.getHeight()):
            for x in xrange(self.getWidth()):
                if self.get(x,y)==">":
                    return (x,y)

    # Get the x,y of the current location
    def getLocation(self):
        location = None
        for y in xrange(0,self.getHeight()-1):
            for x in xrange(0,self.getWidth()-1):
                track = self.get(x,y)
                sigma = len(self.getConnections(x,y,track))
                if track == ">":
                    if sigma==0:
                        location = (x,y)
                    sigma = 0
                if sigma == 1:
                    return (x,y)
        if location != None:
            return location
        raise ValueError('No location found in map\n'+self.getDisplay())

    # Get the terrian at x,y
    def get(self,x,y):
        return self.indexableMap[y][x]

    # Set the terrain at x,y
    # (non-destructive)
    def set(self,x,y,value):
        newMap = [[i for i in row] for row in self.indexableMap]
        newMap[y][x] = value
        return "\n".join(["".join(x) for x in newMap])

    # Get the track connectioning to a piece of track at x,y
    def getConnections(self,x,y,track):
        connections = []
        tracks = []
        for a,b in set(permutations([-1,-1,0,1,1],2)):
            outtrack = self.get(x+a,y+b)
            if Map.isTrack(outtrack) and Map.isConnected("",0,0,track,a,b,outtrack):
                tracks+=[[outtrack,a,b]]
        if len(tracks)==1:return [tracks[0][0]]
        if len(tracks)==0:return []

        for inner,outer in permutations(tracks,2):
            intrack,relXin,relYin = inner
            other,relX,relY = outer
            ex = x + relX
            ey = y + relY
            if Map.isConnected(intrack,relXin,relYin,track,relX,relY,other):
                if other == "M":
                    if len(self.getConnections(ex,ey,other))>=1:
                        connections.append(other)
                else:
                    connections.append(other)
        return connections

    # Is could a piece of track at x,y build in
    # the direct of relX,relY?
    def isBlocked(self,x,y,relX,relY):
        if relX==0 or relY==0:
            return False
        side1 = self.get(x+relX,y)
        side2 = self.get(x,y+relY)
        return (Map.isTrack(side1) or side1=="M")  and (Map.isTrack(side2) or side2=="M")

Updates

  • -560 [17-03-31] A bunch of basic regex golfing
  • +982 [17-03-31] Fixed illegal track laying. Thanks @fəˈnɛtɪk!
  • -99 [17-03-31] Utilized ;s

NonlinearFruit

Posted 2016-12-28T22:01:03.940

Reputation: 5 334

Change some variable names for moar golf ;) – Matthew Roh – 2017-04-02T00:35:15.837

6You should be able to golf this more by using a combination of spaces and tabs for indentation – John Dvorak – 2017-04-02T07:35:18.580

2The two lines starting with elif e!=""and e in"MX>" could be combined into a single line with a ternary if else. Also, some of your defs could be lambdas. Like def A(s):return str(s) can be A=lambda s:str(s), or if you change from __str__ to __repr__, you can use A=lambda s:\s``, at which point, it's not even be worth having A as its own function, since it requires parentheses to call. Just use backticks instead. – mbomb007 – 2017-04-14T16:06:21.100

The code attempts illegal moves when it builds bridges. I can't say for certain this is an issue because it ends the test cases with valid paths. – fəˈnɛtɪk – 2017-04-15T17:28:17.957

What! I had no idea this was made. I was trying to do this and never finished but good job! – Christopher – 2017-04-20T10:51:30.373