Do day 3.

README.md

@@ -2,3 +2,5 @@
 
 - Day 1: 40:00 (I don't know what I am doing.)
 - Day 2: 14:15 (Okay, but far way from leaderboard.)
+- Day 3: 1st 20:00, 2nd 70:00... (I had a logic error that took me a while to find.) 
+- Day 4: 

d3.py

@@ -0,0 +1,101 @@
+import re
+
+NUMBERS = "0123456789"
+EXAMPLE = """
+467..114..
+...*......
+..35..633.
+......#...
+617*......
+.....+.58.
+..592.....
+......755.
+...$.*....
+.664.598..
+"""
+
+def clean(text: str) -> list[str]:
+    return list(filter(lambda l: l.strip() != "", text.splitlines()))
+
+def is_adj_to_symbol(x, y, lines):
+    non_symbol = re.compile(r"[^0-9\.]")
+    for xo, yo in [(-1, -1), (-1, 0), (-1, 1), (0, -1), (0, 1), (1, -1), (1, 0), (1, 1)]:
+        try:
+            if x + xo < 0 or y + yo < 0:
+                continue
+            if non_symbol.match(lines[y + yo][x + xo]):
+                return True
+        except IndexError:
+            pass
+    return False
+
+def solve(lines: list[str]):
+    d = ""
+    adj_to_symbol = False
+    s = 0
+    for (y, line) in enumerate(lines):
+        for (x, c) in enumerate(line):
+            if c not in NUMBERS:
+                if len(d) > 0 and adj_to_symbol:
+                    s += int(d)
+                d = ""
+                adj_to_symbol = False
+            else:
+                if is_adj_to_symbol(x, y, lines):
+                    adj_to_symbol = True
+                d = d + c
+    return s
+
+def get_entire_number(x, y, lines):
+    assert(lines[y][x] in NUMBERS)
+    x_start = x - 1
+    while lines[y][x_start] in NUMBERS and x_start >= 0:
+        x_start -= 1
+    x_start += 1
+    x_start_orig = x_start
+    r = ""
+    while x_start < len(lines[0]) and lines[y][x_start] in NUMBERS:
+        r += lines[y][x_start]
+        x_start += 1
+    return x_start_orig, int(r)
+
+def find_sourrounding_numbers(x, y, lines):
+    full_coords = []
+    numbers = []
+    for xo, yo in [(-1, -1), (0, -1), (1, -1), (-1, 0), (1, 0), (-1, 1), (0, 1), (1, 1)]:
+        new_x = x + xo
+        new_y = y + yo
+        if new_x < 0 or new_y < 0 or new_x >= len(lines[0]) or new_y >= len(lines):
+            continue
+        if lines[new_y][new_x] in NUMBERS:
+            x_start_orig, n = get_entire_number(new_x, new_y, lines)
+            if (x_start_orig, new_y, n) not in full_coords:
+                numbers.append(n)
+                full_coords.append((x_start_orig, y + yo, n))
+    return numbers
+
+def solve2(lines: list[str]):
+    s = 0
+    for (y, line) in enumerate(lines):
+        for (x, c) in enumerate(line):
+            if c == '*':
+                numbers = find_sourrounding_numbers(x, y, lines)
+                if len(numbers) == 2:
+                    # print(numbers)
+                    s += numbers[0] * numbers[1]
+    return s
+
+def main():
+    example = clean(EXAMPLE)
+    print("Example  1:", solve(example))
+    data = clean(open("i3.txt").read())
+    print("Solution 1:", solve(data))
+
+    example = clean(EXAMPLE)
+    print("Example  2:", solve2(example))
+
+    data = clean(open("i3.txt").read())
+    print("Solution 2:", solve2(data))
+
+if __name__ == "__main__":
+    main()

d4.py

@@ -0,0 +1,40 @@
+import re
+
+EXAMPLE = """
+
+"""
+
+def clean(text: str) -> list[str]:
+    return list(filter(lambda l: l.strip() != "", text.splitlines()))
+
+def solve(lines: list[str]):
+    s = 0
+    for (i, line) in enumerate(lines):
+        print(i, line)
+    return s
+
+def solve2(lines: list[str]):
+    s = 0
+    for (i, line) in enumerate(lines):
+        print(i, line)
+    return s
+
+def main():
+    example = clean(EXAMPLE)
+    print("Example  1:", solve(example))
+    return
+
+    data = clean(open("i4.txt").read())
+    print("Solution 1:", solve(data))
+    return
+
+    example = clean(EXAMPLE)
+    print("Example  2:", solve2(example))
+    return
+
+    data = clean(open("i4.txt").read())
+    print("Solution 2:", solve2(data))
+    return
+
+if __name__ == "__main__":
+    main()