2 files changed, 135 insertions, 0 deletions
diff --git a/19/input/24 b/19/input/24
new file mode 100644
index 0000000..0505ca8
--- /dev/null
+++ b/19/input/24
@@ -0,0 +1,5 @@
+#..##
+#.#..
+#...#
+##..#
+#..##
diff --git a/19/py/d24.py b/19/py/d24.py
new file mode 100644
index 0000000..b747986
--- /dev/null
+++ b/19/py/d24.py
@@ -0,0 +1,130 @@
+class hashdict(dict):
+    """
+    hashable dict implementation, suitable for use as a key into
+    other dicts.
+
+        >>> h1 = hashdict({"apples": 1, "bananas":2})
+        >>> h2 = hashdict({"bananas": 3, "mangoes": 5})
+        >>> h1+h2
+        hashdict(apples=1, bananas=3, mangoes=5)
+        >>> d1 = {}
+        >>> d1[h1] = "salad"
+        >>> d1[h1]
+        'salad'
+        >>> d1[h2]
+        Traceback (most recent call last):
+        ...
+        KeyError: hashdict(bananas=3, mangoes=5)
+
+    based on answers from
+       http://stackoverflow.com/questions/1151658/python-hashable-dicts
+
+    """
+    def __key(self):
+        return tuple(sorted(self.items()))
+    def __repr__(self):
+        return "{0}({1})".format(self.__class__.__name__,
+            ", ".join("{0}={1}".format(
+                    str(i[0]),repr(i[1])) for i in self.__key()))
+
+    def __hash__(self):
+        return hash(self.__key())
+    def __setitem__(self, key, value):
+        raise TypeError("{0} does not support item assignment"
+                         .format(self.__class__.__name__))
+    def __delitem__(self, key):
+        raise TypeError("{0} does not support item assignment"
+                         .format(self.__class__.__name__))
+    def clear(self):
+        raise TypeError("{0} does not support item assignment"
+                         .format(self.__class__.__name__))
+    def pop(self, *args, **kwargs):
+        raise TypeError("{0} does not support item assignment"
+                         .format(self.__class__.__name__))
+    def popitem(self, *args, **kwargs):
+        raise TypeError("{0} does not support item assignment"
+                         .format(self.__class__.__name__))
+    def setdefault(self, *args, **kwargs):
+        raise TypeError("{0} does not support item assignment"
+                         .format(self.__class__.__name__))
+    def update(self, *args, **kwargs):
+        raise TypeError("{0} does not support item assignment"
+                         .format(self.__class__.__name__))
+    # update is not ok because it mutates the object
+    # __add__ is ok because it creates a new object
+    # while the new object is under construction, it's ok to mutate it
+    def __add__(self, right):
+        result = hashdict(self)
+        dict.update(result, right)
+        return result
+
+def inside(p):
+    return 0 <= p[0] < 5 and 0 <= p[1] < 5
+
+def neighbours(p):
+    return [(p[0]+1, p[1]), (p[0]-1, p[1]), \
+            (p[0], p[1]+1), (p[0], p[1]-1)]
+
+def draw(bugs):
+    s = ""
+    for y in range(5):
+        s += "\n"
+        for x in range(5):
+            if bugs[(x,y)] == True:
+                s += "#"
+            else:
+                s += "."
+    return s
+
+def draw_nums(bugs):
+    s = ""
+    for y in range(5):
+        s += "\n"
+        for x in range(5):
+            s += str(bugs.get((x,y), 0))
+    return s
+
+def nums(bugs):
+    nums = {}
+    for y in range(5):
+        for x in range(5):
+            p = (x,y)
+            if bugs[p] == True:
+                for n in neighbours(p):
+                    if inside(n):
+                        nums[n] = nums.get(n, 0) + 1
+    return nums
+
+f = open("../input/24", "r").readlines()
+
+bugs = {}
+for y in range(5):
+    for x in range(5):
+        bugs[(x,y)] = (f[y][x] == "#")
+
+seen = set()
+while True:
+    h = hashdict(bugs.copy())
+    if h in seen:
+        break
+    seen.add(h)
+    new = {}
+    ns = nums(bugs)
+    for y in range(5):
+        for x in range(5):
+            p = (x,y)
+            n = ns.get(p, 0)
+            if bugs[p] == False and (n == 1 or n == 2):
+                new[p] = True
+            elif bugs[p] == True and n != 1:
+                new[p] = False
+            else:
+                new[p] = bugs[p]
+    bugs = new
+print(draw(bugs))
+
+ans = 0
+for k, v in bugs.items():
+    if v == True:
+        ans += 2**(k[1]*5 + k[0])
+print(ans)