diff --git a/data/example/2019/04.txt b/data/example/2019/04.txt
new file mode 100644
index 000000000..c6e7396
--- /dev/null
+++ b/data/example/2019/04.txt
@@ -0,0 +1 @@
+229228-249228
diff --git a/src/solution/year_2019/day_04.py b/src/solution/year_2019/day_04.py
new file mode 100644
index 000000000..aa2e6f3
--- /dev/null
+++ b/src/solution/year_2019/day_04.py
@@ -0,0 +1,66 @@
+from typing import Any
+
+
+def _test_len(s: str, n: int):
+    return len(s) == n
+
+
+def _test_increasing(s: str):
+    return all(s[i - 1] <= s[i] for i in range(1, len(s)))
+
+
+def _test_adjacent(s: str):
+    return any(s[i - 1] == s[i] for i in range(1, len(s)))
+
+
+def _get_index(s: str, i: int) -> str | None:
+    if not (0 <= i < len(s)):
+        return None
+
+    return s[i]
+
+
+def _test_adjacent_2(s: str) -> bool:
+    for i in range(1, len(s)):
+        s1 = s[i]
+        s2 = s[i - 1]
+
+        s0 = _get_index(s, i - 2)
+        s3 = _get_index(s, i + 1)
+
+        if s1 == s2 and s1 != s0 and s2 != s3:
+            return True
+
+    return False
+
+
+def _is_valid_password(n: int) -> bool:
+    s = str(n)
+    return all([_test_len(s, 6), _test_adjacent(s), _test_increasing(s)])
+
+
+def _is_valid_password_2(n: int) -> bool:
+    s = str(n)
+    return all([_test_len(s, 6), _test_adjacent_2(s), _test_increasing(s)])
+
+
+def part_1(input_data: str) -> Any:
+    a, b = input_data.split("-")
+    a, b = int(a), int(b)
+
+    return len([x for x in range(a, b + 1) if _is_valid_password(x)])
+
+
+def part_2(input_data: str) -> Any:
+    a, b = input_data.split("-")
+    a, b = int(a), int(b)
+
+    return len([x for x in range(a, b + 1) if _is_valid_password_2(x)])
+
+
+def test_part_1(example_data):
+    assert part_1(example_data) == 316
+
+
+def test_part_2(example_data):
+    assert part_2(example_data) == 218