Initial commit

2024/16/two_opti.py

@@ -0,0 +1,111 @@
+#!/usr/bin/env python3
+
+import pprint
+import sys
+
+input_file = sys.argv[1]
+
+with open(input_file) as fd:
+    lines = [line.rstrip() for line in fd.readlines()]
+
+height = len(lines)
+width = len(lines[0])
+
+vec = tuple[int, int]
+
+directions = [
+    (-1, 0),  # ^ North
+    (0, 1),  # > East
+    (1, 0),  # v South
+    (0, -1),  # < West
+]
+
+directions_keys = ("^", ">", "v", "<")
+
+min_scores: list[list[list[None | int]]] = list()
+for _ in range(height):
+    line: list[list[None | int]] = list()
+    for _ in range(width):
+        cell: list[None | int] = [None] * len(directions)
+        line.append(cell)
+    min_scores.append(line)
+
+start = height - 2, 1
+
+valid_paths: list[tuple[int, set[vec]]] = list()
+
+
+def walk(pos: vec, dir: int, score: int, path: list[vec]) -> int | None:
+    i, j = pos
+    char = lines[i][j]
+
+    depth = len(path)
+    path = path + [pos]
+
+    if depth > 1000:
+        return None
+
+    # print("-" * depth, 28, pos, char, directions_keys[dir], score)
+    if char == "E":
+        valid_paths.append((score, set(path)))
+        return score
+    elif char == "#":
+        return None
+
+    min_score = min_scores[i][j][dir]
+    for d, min_score in enumerate(min_scores[i][j]):
+        if min_score is None:
+            continue
+        if d == dir:
+            if score > min_score:
+                return None
+        else:
+            if score > min_score + 1000:
+                return None
+    min_scores[i][j][dir] = score
+
+    mscore = None
+    for ndir, direction in enumerate(directions):
+        ii, jj = i + direction[0], j + direction[1]
+        price = 1 if dir == ndir else 1001
+        nscore = walk((ii, jj), ndir, score + price, path)
+        if nscore is None:
+            continue
+        if mscore is None or nscore < mscore:
+            mscore = nscore
+    return mscore
+
+
+sys.setrecursionlimit(9000)
+tot_score = walk(start, 1, 0, [])
+
+print(76, len(valid_paths))
+all_best: set[vec] = set()
+for s, path in valid_paths:
+    if s != tot_score:
+        continue
+    print(81, "BEST")
+    all_best |= path
+
+# Viz
+for i in range(height):
+    cline = ""
+    for j in range(width):
+        char = lines[i][j]
+        pos = i, j
+        if pos in all_best:
+            min_score = None
+            for d in range(len(directions)):
+                score = min_scores[i][j][d]
+                if score is None:
+                    continue
+                if min_score is None or score < min_score:
+                    char = directions_keys[d]
+                    min_score = score
+        cline += char
+    print(cline)
+print()
+
+
+print(tot_score)
+print(len(all_best))