du premier coup

2023/day3/main.py

@@ -1,3 +1,6 @@
+from functools import reduce
+
+
 def part1(file: str):
     acc = []
     with open(file) as f:
@@ -60,13 +63,84 @@ def part1(file: str):
     return res
 
 
-""" def part2(file: str):
-    pass """
+def part2(file: str):
+    acc = []
+    default = (-1, 0)
+    bad = (-2, 0)
+    with open(file) as f:
+        for line in f:
+            acc.append([(c, default) for c in line if c != "\n"])
+
+    for i1, r in enumerate(acc):
+        for i2, c in enumerate(r):
+            if not c[0].isdigit():
+                continue
+
+            def checker(a: int, b: int, check: tuple[int, int]):
+                # Sanity check
+                if a < 0 or len(acc) <= a:
+                    return check
+                if b < 0 or len(acc[a]) <= b:
+                    return check
+
+                # Adjacency check
+                if acc[a][b][0] == "*":
+                    # If already set
+                    if check[0] >= 0 or check[0] == -2:
+                        # Shouldn't be multiplied more than 2, if already encountered:
+                        #   Ignore the number
+                        return bad
+                    return a, b
+
+                return check
+
+            # Coordinates
+            check = default
+            for i in range(-1, 2):
+                for j in range(-1, 2):
+                    if i == 0 and j == 0:
+                        continue
+                    check = checker(i1 + i, i2 + j, check)
+
+            acc[i1][i2] = (c[0], check)
+
+    # Find problems
+    buffer = ""
+    res = []
+    for lines in acc:
+        test = default
+        for i, (c, star_pos) in enumerate(lines):
+            if c.isdigit():
+                buffer += c
+                # test déjà défini + différente star
+                if test != default and star_pos != test and star_pos != default:
+                    test = bad
+                # test pas défini + star ok
+                if test == default and star_pos != bad:
+                    test = star_pos
+
+            # End of number
+            if not c.isdigit() or i + 1 >= len(lines):
+                if len(buffer) > 0:
+                    if test != default and test != bad:
+                        res.append((int(buffer), test))
+                test = default
+                buffer = ""
+
+    ratios = {}
+    for number, values in res:
+        try:
+            ratios[f"{values}"].append(number)
+        except KeyError:
+            ratios[f"{values}"] = [number]
+    return sum(
+        reduce(lambda x, y: x * y, gear) for gear in ratios.values() if len(gear) > 1
+    )
 
 
 if __name__ == "__main__":
     assert part1("example.txt") == 4361
     print(part1("input.txt"))
 
-    """ assert part2("example.txt") == 2286
-    print(part2("input.txt")) """
+    assert part2("example.txt") == 467835
+    print(part2("input.txt"))