Day 05

day05/part2.py

@@ -0,0 +1,81 @@
+#!/usr/bin/env python3
+from typing import List, Tuple
+from tqdm import tqdm
+
+lines = (x.strip() for x in open("input.txt"))
+seeds = ()
+current_map = "undef"
+maps = {}
+map_names = []
+
+for line in lines:
+    match line:
+        case "" | "\n":
+            continue
+        case x if x.startswith("seeds: "):
+            rest = x[len("seeds: "):]
+            seeds = tuple(int(y) for y in rest.split(" "))
+        case x if x.endswith(" map:"):
+            rest = x[:-len(" map:")]
+            current_map = rest
+            maps[current_map] = []
+            map_names.append(current_map)
+        case x if len(x) and x[0].isdigit():
+            maps[current_map].append(tuple(int(y) for y in x.split(" ")))
+        case _:
+            pass
+
+def parse_map(value: List[Tuple[int, int, int]]):
+    curr = 0
+    out = []
+    for dest, src, size in sorted(value, key=lambda x: x[1]):
+        if src > curr:
+            out.append((curr, 0))
+        if size > 0:
+            out.append((src, dest-src))
+        curr = src + size
+    out.append((curr, 0))
+    return out
+
+maps = {name: parse_map(value) for name, value in maps.items()}
+
+def find_largest_smaller_value(sorted_list, x):
+    low, high = 0, len(sorted_list)
+
+    while low < high - 1:
+        mid = (low + high) // 2
+        if sorted_list[mid][0] <= x:
+            low = mid
+        else:
+            high = mid
+
+    return sorted_list[low], low
+
+
+def merge_list(curr_map, next_map):
+    next_mapping = []
+    for i in range(0, len(curr_map)):
+        dest_start = curr_map[i][0] + curr_map[i][1]
+        dest_start_idx = find_largest_smaller_value(next_map, dest_start)[1]
+        dest_end = curr_map[i + 1][0] + curr_map[i][1] - 1 if i + 1 < len(curr_map) else None
+        dest_end_idx = find_largest_smaller_value(next_map, dest_end)[1] if dest_end is not None else len(next_map) - 1
+        for next_start, next_offset in next_map[dest_start_idx:dest_end_idx + 1]:
+            next_mapping.append((max(curr_map[i][0], next_start - curr_map[i][1]), curr_map[i][1] + next_offset))
+    return next_mapping
+
+# merge lists into a single one
+curr_map = maps[map_names[0]]
+for name in map_names[1:]:
+    curr_map = merge_list(curr_map, maps[name])
+
+
+result = float("inf")
+for i in range(0, len(seeds), 2):
+    dest_start = seeds[i]
+    dest_start_idx = find_largest_smaller_value(curr_map, dest_start)[1]
+    dest_end = seeds[i] + seeds[i+1] - 1
+    dest_end_idx = find_largest_smaller_value(curr_map, dest_end)[1]
+    for next_start, next_offset in curr_map[dest_start_idx:dest_end_idx + 1]:
+        result = min(result, next_start + next_offset)
+
+print(result)