From d0881dabdf7042cb13ef91624e16d40dccce0deb Mon Sep 17 00:00:00 2001
From: Valentin Gehrke <madmaurice@zom.bi>
Date: Tue, 28 Apr 2015 23:16:52 +0200
Subject: [PATCH] Wolf Sheep Cabbage Simulator

---
 wolfsheep.py | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 wolfsheep.py

diff --git a/wolfsheep.py b/wolfsheep.py
new file mode 100644
index 0000000..8596e5c
--- /dev/null
+++ b/wolfsheep.py
@@ -0,0 +1,56 @@
+class Model:
+    Man = "M"
+    Wolf = "W"
+    Sheep = "S"
+    Cabbage = "C"
+    def __init__(self, left, right):
+        self.left = set(left)
+        self.right = set(right)
+
+    def __eq__(self,other):
+        return other.left == self.left and other.right == self.right
+
+    def __repr__(self):
+        return "(%s,%s)" % ( repr(self.left), repr(self.right))
+
+    def pretty(self):
+        return ",".join(self.left) + " <-> " + ",".join(self.right)
+
+class Simulator:
+    def simulate(self, state, stack=[]):
+        #stack.append(state)
+        stack = stack + [state]
+        if state.right == set([Model.Man,Model.Wolf,Model.Sheep,Model.Cabbage]):
+            return stack
+
+        nextStates = []
+        if Model.Man in state.left:
+            for obj in state.left:
+                nextStates.append( Model(state.left - set([Model.Man,obj]) , state.right | set([Model.Man,obj]) ) )
+        else:
+            for obj in state.right:
+                nextStates.append( Model(state.left | set([Model.Man, obj]) , state.right - set([Model.Man,obj]) ) )
+
+        nextStates = list(filter(
+                lambda s: s not in stack and not(
+                    ( (set([Model.Wolf,Model.Sheep]) <= s.left or set([Model.Sheep, Model.Cabbage]) <= s.left) and Model.Man not in s.left ) or
+                    ( (set([Model.Wolf,Model.Sheep]) <= s.right or set([Model.Sheep, Model.Cabbage]) <= s.right) and Model.Man not in s.right )
+                )
+            , nextStates)) #Remove invalid and previous states.
+        #print("%s: %s\nstack: %s" % (state,nextStates,stack))
+
+        for s in nextStates:
+            m = self.simulate(s,stack)
+            if m is not None:
+                return m
+
+        return None
+
+
+if __name__ == "__main__":
+    sim = Simulator()
+    result = sim.simulate(Model([Model.Man, Model.Wolf, Model.Sheep, Model.Cabbage],[]))
+    i = 0
+    for state in result:
+        print("%d: %s" % (i,state.pretty()))
+        i+=1