diff --git a/12/a.py b/12/a.py
new file mode 100644
index 0000000..2ca7a82
--- /dev/null
+++ b/12/a.py
@@ -0,0 +1,52 @@
+class Node(object):
+    def __init__(self, name):
+        self.name = name
+        self.links = []
+        self.small = self.name == self.name.lower()
+
+    def __repr__(self):
+        return "<{}>".format(self.name)
+
+
+nodes = {}
+
+
+# with open("sample.txt") as f:
+with open("input.txt") as f:
+    for line in f.readlines():
+        a, b = line.strip().split("-")
+        if a not in nodes:
+            nodes[a] = Node(a)
+        if b not in nodes:
+            nodes[b] = Node(b)
+        nodes[a].links.append(nodes[b])
+        nodes[b].links.append(nodes[a])
+
+
+paths = []
+
+
+def step(node, path, visited):
+    # append node to the path
+    path.append(node)
+
+    # if we just hit the end, emit the path
+    if node.name == "end":
+        paths.append(path)
+        return
+
+    # append node to visited
+    if node.small:
+        visited.update([node.name])
+
+    # look for legal next nodes
+    legal = [n for n in node.links if n.name not in visited]
+
+    # call step for each
+    for next_step in legal:
+        step(next_step, path[:], set(visited))
+
+
+step(nodes["start"], [], set())
+
+print(len(paths))
diff --git a/12/b.py b/12/b.py
new file mode 100644
index 0000000..8a756f5
--- /dev/null
+++ b/12/b.py
@@ -0,0 +1,64 @@
+from collections import defaultdict
+
+
+class Node(object):
+    def __init__(self, name):
+        self.name = name
+        self.links = []
+        self.small = self.name == self.name.lower()
+
+    def __repr__(self):
+        return "<{}>".format(self.name)
+
+
+nodes = {}
+
+
+# with open("sample.txt") as f:
+with open("input.txt") as f:
+    for line in f.readlines():
+        a, b = line.strip().split("-")
+        if a not in nodes:
+            nodes[a] = Node(a)
+        if b not in nodes:
+            nodes[b] = Node(b)
+        nodes[a].links.append(nodes[b])
+        nodes[b].links.append(nodes[a])
+
+
+paths = []
+
+
+def step(node, path, visited):
+    # append node to the path
+    path.append(node)
+
+    # if we just hit the end, emit the path
+    if node.name == "end":
+        paths.append(path)
+        return
+
+    # append node to visited
+    if node.small:
+        visited[node.name] += 1
+
+    # look for legal next nodes
+    legal = [n for n in node.links if n.name not in visited]
+
+    # call step for each
+    for next_step in legal:
+        step(next_step, path[:], defaultdict(lambda: 0, visited))
+
+    # use a small cave a second time, if possible
+    if all([v <= 1 for v in visited.values()]):
+        legal = [n for n in node.links if n.name in visited and n.small and n != nodes["start"]]
+
+        for next_step in legal:
+            step(next_step, path[:], defaultdict(lambda: 0, visited))
+
+
+step(nodes["start"], [], defaultdict(lambda: 0))
+
+print(len(paths))
+
+#35m
diff --git a/12/input.txt b/12/input.txt
new file mode 100644
index 0000000..4a1ba87
--- /dev/null
+++ b/12/input.txt
@@ -0,0 +1,22 @@
+FK-gc
+gc-start
+gc-dw
+sp-FN
+dw-end
+FK-start
+dw-gn
+AN-gn
+yh-gn
+yh-start
+sp-AN
+ik-dw
+FK-dw
+end-sp
+yh-FK
+gc-gn
+AN-end
+dw-AN
+gn-sp
+gn-FK
+sp-FK
+yh-gc
diff --git a/12/sample.txt b/12/sample.txt
new file mode 100644
index 0000000..898cd56
--- /dev/null
+++ b/12/sample.txt
@@ -0,0 +1,7 @@
+start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end
\ No newline at end of file