Solve day 4 (Python)

q2.py

@@ -0,0 +1,49 @@
+def q1(text: str):
+    levels = text.splitlines()
+
+    count = 0
+    for level in levels:
+        curr = [int(l) for l in level.split()]
+
+        increasing = all(curr[i] < curr[i + 1] for i in range(len(curr) - 1))
+        decreasing = all(curr[i] > curr[i + 1] for i in range(len(curr) - 1))
+        diff_criterion = all(
+            1 <= abs(curr[i] - curr[i + 1]) <= 3 for i in range(len(curr) - 1)
+        )
+
+        count += 1 if diff_criterion and (increasing or decreasing) else 0
+
+    return count
+
+
+def q2(text: str):
+    levels = text.splitlines()
+
+    count = 0
+    for level in levels:
+        curr = [int(l) for l in level.split()]
+
+        for i in range(len(curr) + 1):
+            curr_i = curr.copy()
+            if i < len(curr):
+                del curr_i[i]
+
+            increasing = all(curr_i[i] < curr_i[i + 1] for i in range(len(curr_i) - 1))
+            decreasing = all(curr_i[i] > curr_i[i + 1] for i in range(len(curr_i) - 1))
+            diff_criterion = all(
+                1 <= abs(curr_i[i] - curr_i[i + 1]) <= 3 for i in range(len(curr_i) - 1)
+            )
+
+            if diff_criterion and (increasing or decreasing):
+                count += 1
+                break
+
+    return count
+
+
+if __name__ == "__main__":
+    with open("i2.txt") as f:
+        text = f.read()
+
+    print(q1(text))
+    print(q2(text))

q3.py

@@ -0,0 +1,33 @@
+import re
+
+MUL_PATTERN = re.compile(r"mul\((\d+), *(\d+)\)")
+def task1(text: str) -> int:
+    total = 0
+    for mul in MUL_PATTERN.finditer(text):
+        a, b = map(int, mul.groups())
+        total += a*b
+    return total
+
+MUL_OR_DO_PATTERN = re.compile(r"do\(\)|don't\(\)|mul\((\d+), *(\d+)\)")
+def task2(text: str) -> int:
+    total = 0
+    on = True
+    for op in MUL_OR_DO_PATTERN.finditer(text):
+        if op.group(0) == "do()":
+            on = True
+        if op.group(0) == "don't()":
+            on = False
+        if op.group(1) and on:
+            a, b = map(int, op.groups())
+            total += a*b
+    return total
+
+def main():
+    with open("i3.txt") as f:
+        text = f.read()
+
+    print(task1(text))
+    print(task2(text))
+
+if __name__ == "__main__":
+    main()

q4.py

@@ -0,0 +1,79 @@
+from typing import Iterable
+
+WORD = "XMAS"
+def words_from_grid(grid, startx, starty) -> Iterable[str]:
+    num_rows = len(grid)
+    num_cols = len(grid[0])
+
+    for (dx, dy) in (
+        (1, 0), (-1, 0),
+        (0, 1), (0, -1),
+        (1, 1), (-1, 1),
+        (1, -1), (-1, -1)
+    ):
+        x = startx
+        y = starty
+        word = ""
+        for i in range(len(WORD)):
+            if x >= num_cols or x < 0:
+                continue
+            if y >= num_rows or y < 0:
+                continue
+
+            word += grid[y][x]
+            x += dx
+            y += dy
+
+        yield word
+
+def cross_words_from_grid(grid, startx, starty) -> tuple[str, str]:
+    num_rows = len(grid)
+    num_cols = len(grid[0])
+
+    output = []
+    for (dx, dy) in (
+        (1, 1), (1, -1)
+    ):
+        x = startx - dx
+        y = starty - dy
+        word = ""
+        for _ in range(3):
+            if x >= num_cols or x < 0:
+                continue
+            if y >= num_rows or y < 0:
+                continue
+
+            word += grid[y][x]
+            x += dx
+            y += dy
+        output.append(word)
+    # o: tuple[str, str] = 
+    return tuple(output)
+
+def task1(grid: list[str]) -> int:
+    count = 0
+    for y in range(len(grid)):
+        for x in range(len(grid[0])):
+            for word in words_from_grid(grid, x, y):
+                if word == WORD or word == str(reversed(WORD)):
+                    count += 1
+    return count
+
+def task2(grid: list[str]) -> int:
+    count = 0
+    for y in range(len(grid)):
+        for x in range(len(grid[0])):
+            leading, anti = cross_words_from_grid(grid, x, y)
+            if (leading == "MAS" or leading == "SAM") and (anti == "MAS" or anti == "SAM"):
+                count += 1
+    return count
+
+# I can't believe I got both parts first try... this should've been a very error-prone episode!
+def main():
+    with open("i4.txt") as f:
+        text = f.read().splitlines()
+    print(task1(text))
+    print(task2(text))
+
+if __name__ == "__main__":
+    main()