import 2023 aoc

2023/day5/day5.py

@@ -0,0 +1,70 @@
+from itertools import zip_longest
+
+
+def grouper(n, iterable):
+    "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx"
+    args = [iter(iterable)] * n
+    return zip_longest(*args)
+
+
+def part1(sections):
+    # consume seed section
+    _, seeds = next(sections)
+    seeds = [int(s) for s in seeds]
+    for _, mapping in sections:
+        seeds = [apply_mapping(s, mapping) for s in seeds]
+    print(f"Part 1, lowest location number = {min(seeds)}")
+
+
+def part2(sections):
+    # consume seed section
+    _, seeds = next(sections)
+    seeds = [int(s) for s in seeds]
+
+    min_seed = 2**128
+    for start_seed, length in grouper(2, seeds):
+        subseeds = range(start_seed, start_seed + length)
+        print(f"calculate_for_subseeds(subseeds len={len(subseeds)})")
+        res = calculate_for_subseeds(subseeds, sections)
+        mini = min(res)
+        if mini < min_seed:
+            min_seed = mini
+    
+    print(f"Part 2 {min_seed}")
+
+
+def calculate_for_subseeds(seeds, sections):
+    new_seeds = seeds
+    for _, mapping in sections:
+        new_seeds = [apply_mapping(s, mapping) for s in new_seeds]
+    return new_seeds
+
+
+def apply_mapping(seed, mapping):
+    for dst, src, length in grouper(3, mapping):
+        src, length, dst = int(src), int(length), int(dst)
+        end = src + length
+        if src <= seed < end:
+            return seed + (dst-src)
+    return seed
+
+
+def parse_input(infile):
+    with open(infile) as f:
+        sections = f.read().split("\n\n")
+        sections = ((title, numbers) for title, numbers in (s.split(":") for s in sections))
+        sections = ((title, numbers.split()) for title, numbers in sections)
+        return sections
+
+
+if __name__ == "__main__":
+    import sys
+    import os
+    SCRIPTPATH = os.path.dirname(os.path.realpath(__file__))
+
+    infile = next(iter(sys.argv[1:]), None)
+    sections = parse_input(infile or os.path.join(SCRIPTPATH, "example.txt"))
+    part1(sections)
+    sections = parse_input(infile or os.path.join(SCRIPTPATH, "example.txt"))
+    part2(sections)
+