求助：Advent of Code 2023 Day17 Part2代码测通但输入报错

我在解决Advent of Code 2023第17天第二部分问题时，第一部分能得到正确答案，但修改代码适配第二部分规则后，针对实际输入的答案错误，不过代码能通过题目提供的测试用例，实在找不到问题所在。

可能的问题排查方向 #

• 初始状态仅添加了朝右的节点，缺少朝下的初始节点，可能导致错过更优路径
• closed集合的去重逻辑存在缺陷：仅用(y, x, 方向, 连续步数)判断是否访问过，但同一状态可能存在更小的代价路径，直接跳过会导致最优解被忽略，应该改用字典记录每个状态的最小代价
• 转向规则验证：检查expand_helper中转向时是否严格执行了"必须连续走满4步才能转向"的要求，是否存在提前转向的情况

以下是我的代码：

from copy import deepcopy
from heapq import heappush, heappop

pInput = [
    [int(char) for char in list(line.replace("\n", ""))]
    for line in open("input.txt", "r")
]
width, height = len(pInput[0]), len(pInput)


def maxStepsReached(steps):
    return steps > 10


def isOOB(y, x):
    return not (0 <= y < len(pInput) and 0 <= x < len(pInput[0]))


def expand_helper(node, dy, dx, dir, res):
    new_y = node[1] + dy
    new_x = node[2] + dx
    if isOOB(new_y, new_x) or dir == node[3] and maxStepsReached(node[4] + 1):
        return res
    if dir == node[3]:
        res.append((node[0] + pInput[new_y][new_x], new_y, new_x, dir, node[4] + 1))
    elif node[4] >= 4:
        res.append((node[0] + pInput[new_y][new_x], new_y, new_x, dir, 1))
    return res


def expand(node):
    res = []
    if node[3] == ">":
        for dy, dx, dir in [[0, 1, ">"], [-1, 0, "A"], [1, 0, "V"]]:
            res = expand_helper(node, dy, dx, dir, res)
    elif node[3] == "<":
        for dy, dx, dir in [[0, -1, "<"], [-1, 0, "A"], [1, 0, "V"]]:
            res = expand_helper(node, dy, dx, dir, res)
    elif node[3] == "A":
        for dy, dx, dir in [[-1, 0, "A"], [0, 1, ">"], [0, -1, "<"]]:
            res = expand_helper(node, dy, dx, dir, res)
    elif node[3] == "V":
        for dy, dx, dir in [[1, 0, "V"], [0, 1, ">"], [0, -1, "<"]]:
            res = expand_helper(node, dy, dx, dir, res)
    return res


def ucs():
    closed = set()
    open = []
    heappush(open, (0, 0, 0, ">", 1))

    while open:
        node = heappop(open)
        if node[1] == height - 1 and node[2] == width - 1 and node[4] >= 4:
            return node[0]
        if (node[1], node[2], node[3], node[4]) in closed:
            continue
        closed.add((node[1], node[2], node[3], node[4]))
        successors = expand(node)
        for s in successors:
            heappush(open, s)

    return -1


print(ucs())

内容的提问来源于stack exchange，提问作者Coder2002