diff --git a/2021/12/README.md b/2021/12/README.md
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+# 12
+
+The first is quite nice, good recursion exercise :)
+I messed up at first as I saved the graph as a directional, but that was a quick fix.
+
+For part 2, since we only visit a single cave once more, we cann add a `joker` parameter to our walker and use it only once when we are stuck in every path of the tree.
+
+<details>
+  <summary>Solutions</summary>
+  <ol>
+    <li>5252</li>
+    <li>147784</li>
+  </ol>
+</details>
diff --git a/2021/12/python/main.py b/2021/12/python/main.py
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+#!/usr/bin/env python
+
+from os.path import dirname, join
+
+# Day 12
+
+# Common
+
+
+def read_input(filename):
+    data = join(dirname(__file__), '..', filename)
+    with open(data) as f:
+        return f.read().strip()
+
+
+test = read_input('test.txt')
+data = read_input('input.txt')
+
+
+class Node:
+    def __init__(self, name: str, children: set['Node']):
+        self.name = name
+        self.children = children
+        self.big = name[0].isupper()
+
+    def isSmall(self) -> bool:
+        return self.name[0].islower()
+
+    def __str__(self) -> str:
+        return f'{self.name} -> {[node.name for node in self.children]}'
+
+    def __repr__(self) -> str:
+        return self.name
+
+
+class Graph:
+    start_node = 'start'
+    end_node = 'end'
+
+    def __init__(self, nodes: list):
+        self.nodes = nodes
+
+    def _find_node(self, name: str) -> Node:
+        for node in self.nodes:
+            if node.name == name:
+                return node
+        raise Exception(f'node "{name}" not found')
+
+    def _find_routes(self, current_node: Node, visited: set[Node], joker: bool) -> list[list[Node]]:
+        routes: list[list[Node]] = []
+
+        # Iterate children
+        for node in current_node.children:
+            if node.name == Graph.start_node:
+                continue
+            if node.name == Graph.end_node:
+                routes.append([node])
+                continue
+
+            # Check if is a small cave -> move on
+            if not node.big and node in visited:
+                # Part 2
+                # If it's already visited, but we still have the "joker" left, we can use it
+                if joker:
+                    routes += self._find_routes(node, {*visited, node}, False)
+                continue
+            routes += self._find_routes(node, {*visited, node}, joker)
+        return [[current_node, *route] for route in routes]
+
+    def find_routes(self, allow_double=False):
+        start_node = self._find_node(Graph.start_node)
+        return self._find_routes(start_node, {start_node}, allow_double)
+
+    @staticmethod
+    def parse(text: str):
+        links = [tuple(link.split('-')) for link in text.splitlines()]
+        nodeNames = set()
+        for link in links:
+            nodeNames.add(link[0])
+            nodeNames.add(link[1])
+        nodes = {
+            name: Node(name, set())
+            for name in nodeNames
+        }
+        for start, end in links:
+            nodes[start].children.add(nodes[end])
+            nodes[end].children.add(nodes[start])
+
+        return Graph(list(nodes.values()))
+
+
+# 1
+print('1.')
+
+graph = Graph.parse(test)
+print(len(graph.find_routes()))
+graph = Graph.parse(data)
+print(len(graph.find_routes()))
+
+# 2
+print('\n2.')
+graph = Graph.parse(test)
+print(len(graph.find_routes(True)))
+graph = Graph.parse(data)
+print(len(graph.find_routes(True)))