From 353b96999bec4b6314d87a579a166a4a2b64665a Mon Sep 17 00:00:00 2001
From: Lukas Winkler <git@lw1.at>
Date: Thu, 5 Dec 2019 15:58:22 +0100
Subject: [PATCH] add day 4

---
 python/4/day4.py      | 55 +++++++++++++++++++++++++++++++++++++++++++
 python/4/test_day4.py | 40 +++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+)
 create mode 100644 python/4/day4.py
 create mode 100644 python/4/test_day4.py

diff --git a/python/4/day4.py b/python/4/day4.py
new file mode 100644
index 0000000..e5c6d64
--- /dev/null
+++ b/python/4/day4.py
@@ -0,0 +1,55 @@
+from collections import Counter
+
+INPUT = "245182-790572"
+
+
+def increasing_digit(number: int) -> bool:
+    prev = 0
+    for char in str(number):
+        if prev > int(char):
+            return False
+        else:
+            prev = int(char)
+    return True
+
+
+def has_adjacent_digits(number: int) -> bool:
+    prev = None
+    for char in str(number):
+        if prev == char and prev is not None:
+            return True
+        else:
+            prev = char
+    return False
+
+
+def has_adjacent_digits_that_arent_part_of_a_larger_group(number: int) -> bool:
+    stats = Counter(str(number))
+    for key, count in stats.items():
+        if count == 2:
+            return True
+    return False
+
+
+def part1() -> int:
+    lower, upper = map(int, INPUT.split("-"))
+    validcount = 0
+    for pw in range(lower, upper + 1):
+        if increasing_digit(pw) and has_adjacent_digits(pw):
+            validcount += 1
+
+    return validcount
+
+def part2() -> int:
+    lower, upper = map(int, INPUT.split("-"))
+    validcount = 0
+    for pw in range(lower, upper + 1):
+        if increasing_digit(pw) and has_adjacent_digits_that_arent_part_of_a_larger_group(pw):
+            validcount += 1
+
+    return validcount
+
+
+if __name__ == '__main__':
+    print(part1())
+    print(part2())
diff --git a/python/4/test_day4.py b/python/4/test_day4.py
new file mode 100644
index 0000000..3374533
--- /dev/null
+++ b/python/4/test_day4.py
@@ -0,0 +1,40 @@
+from day4 import increasing_digit, has_adjacent_digits, part1, has_adjacent_digits_that_arent_part_of_a_larger_group, \
+    part2
+
+
+def test_increasing_digit():
+    assert increasing_digit(1234567)
+    assert not increasing_digit(1236567)
+    assert increasing_digit(1234447)
+
+
+def test_has_adjacent_digits():
+    assert has_adjacent_digits(11345345)
+    assert has_adjacent_digits(343244)
+    assert not has_adjacent_digits(2454367)
+
+
+def test_example_codes():
+    assert has_adjacent_digits(111111) and increasing_digit(111111)
+    assert has_adjacent_digits(223450) and not increasing_digit(223450)
+    assert not has_adjacent_digits(123789) and increasing_digit(123789)
+
+
+def test_has_adjacent_digits_that_arent_part_of_a_larger_group():
+    assert has_adjacent_digits_that_arent_part_of_a_larger_group(11345345)
+    assert has_adjacent_digits_that_arent_part_of_a_larger_group(343244)
+    assert not has_adjacent_digits_that_arent_part_of_a_larger_group(24544467)
+
+
+def test_more_example_codes():
+    assert has_adjacent_digits_that_arent_part_of_a_larger_group(112233)
+    assert not has_adjacent_digits_that_arent_part_of_a_larger_group(123444)
+    assert has_adjacent_digits_that_arent_part_of_a_larger_group(111122)
+
+
+def test_part1():
+    assert part1() == 1099
+
+
+def test_part2():
+    assert part2() == 710