diff --git a/2020/d07/ex1/ex1.py b/2020/d07/ex1/ex1.py
new file mode 100755
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--- /dev/null
+++ b/2020/d07/ex1/ex1.py
@@ -0,0 +1,77 @@
+#!/usr/bin/env python
+
+import re
+import sys
+from collections import defaultdict
+from copy import deepcopy
+from dataclasses import dataclass
+from typing import Dict, List, Set, Tuple
+
+
+@dataclass(eq=True, frozen=True)  # Hashable
+class ColorInfo:
+    num: int
+    color: str
+
+
+Graph = Dict[str, Set[ColorInfo]]
+
+
+def extract_info(line: str) -> Tuple[str, Set[ColorInfo]]:
+    color_pattern = re.compile("(.*) contain ")
+    match = color_pattern.search(line)
+    assert match is not None
+    color = match.group(1).replace("bags", "bag")
+
+    line = line[match.end() : -1]  # Remove period at end of line
+
+    if line == "no other bags":
+        return color, set()
+
+    colors: Set[ColorInfo] = set()
+    pattern = re.compile("([0-9]+) (.*)")
+    for col in line.split(", "):
+        match = pattern.search(col)
+        assert match is not None
+        colors |= {
+            ColorInfo(int(match.group(1)), match.group(2).replace("bags", "bag"))
+        }
+
+    return color, colors
+
+
+def to_graph(raw: List[str]) -> Graph:
+    return {color: inside for color, inside in map(extract_info, raw)}
+
+
+def reverse(graph: Graph) -> Graph:
+    reverse: Graph = defaultdict(set)
+
+    for color, contained in graph.items():
+        for col in contained:
+            reverse[col.color] |= {ColorInfo(-1, color)}
+
+    return reverse
+
+
+def containing(graph: Graph, col: str) -> Set[ColorInfo]:
+    res = deepcopy(graph[col])
+    for contains in graph[col]:
+        res |= containing(graph, contains.color)
+    return res
+
+
+def solve(raw: List[str]) -> int:
+    graph = to_graph(raw)
+    reverse_graph = reverse(graph)
+
+    return len(containing(reverse_graph, "shiny gold bag"))
+
+
+def main() -> None:
+    input = [line.strip() for line in sys.stdin.readlines()]
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()