aoc21/day15-2.py

from queue import PriorityQueue
import sys
import copy

class grid:
    def __init__(self):
        self.y = []
        self.attempts = 0
        self.solutions = 0
        self.current_smallest_solution_level = None
        self.point_costs = {(0, 0): 0}
        self.next_point_queue = PriorityQueue()
        self.next_point_queue.put((0, (0, 0)))
        self.visited = {}

    def addline(self, line):
        self.y.append([int(i) for i in line])
        self.maxy = len(self.y) - 1
        self.maxx = len(self.y[0]) - 1

        # print(self.maxx)
        # print(self.maxy)

    def largegrid(self):
        for f in self.y:
            temp = copy.copy(f)
            for i in range(1, 5):
                for t in range(len(temp)):
                    temp[t] += 1
                    if temp[t] > 9:
                        temp[t] -= 9
                f.extend(temp)
        temp2 = copy.copy(self.y)
        for i in range(1, 5):
            temp3 = copy.copy(temp2)
            for f in temp3:
                self.y.append([(g+i-1) % 9 + 1 for g in f])
        self.maxy = len(self.y) - 1
        self.maxx = len(self.y[0]) - 1

   # def initialpath(self):            

    def findpath(self):
        while not self.next_point_queue.empty():
            level, poi = self.next_point_queue.get()
            if self.visited.get(poi, False):
                continue
            self.visited[poi] = True
            self.attempts += 1
            if self.attempts % 100000 == 0:
                print('Attempt %d, solutions: %d, cost: %d, visited: %d, queued: %d' % (
                    self.attempts, self.solutions, self.current_smallest_solution_level or -1,
                    len(self.visited), self.next_point_queue.qsize()))

            neighbors = self.get_neighbors(poi, level)

            for i in neighbors:
                next_level = level + int(self.y[i[0]][i[1]])
                if (self.current_smallest_solution_level is not None and
                    next_level > self.current_smallest_solution_level):
                    # We already found a solution that was overall less risky
                    # than the current path, so who cares.
                    continue
                if i == (self.maxy, self.maxx):
                    self.solutions += 1
                    if (self.current_smallest_solution_level is None or
                        next_level < self.current_smallest_solution_level):
                        self.current_smallest_solution_level = next_level
                    # print('Found solution: ', i, ', orig level ', level)
                    continue
                elif self.visited.get(i, False) and (i in self.point_costs and self.point_costs[i] <= next_level):
                    # We already visited the point on a cheaper path.
                    continue
                else:
                    # print('Path: %s, next: %s' % (repr(path), i))
                    self.point_costs[i] = next_level
                    self.next_point_queue.put((next_level, i))

            # Try to find a path from the current point to the end by going down and right
            # alternatingly, so we can restrict the search to paths less costly than the
            # current one.
            next_level = level
            while poi != (self.maxx, self.maxy):
                if poi[0] < self.maxx:
                    poi = (poi[0] + 1, poi[1])
                    next_level += int(self.y[poi[0]][poi[1]])
                    if poi in self.point_costs and next_level > self.point_costs[poi]:
                        break
                    self.point_costs[poi] = next_level
                    
                if poi[1] < self.maxy:
                    poi = (poi[0], poi[1] + 1)
                    next_level += int(self.y[poi[0]][poi[1]])
                    if poi in self.point_costs and next_level > self.point_costs[poi]:
                        break
                    self.point_costs[poi] = next_level

                if poi == (self.maxx, self.maxy):
                    self.solutions += 1
                    if (self.current_smallest_solution_level is None or
                        next_level < self.current_smallest_solution_level):
                        self.current_smallest_solution_level = next_level


    def get_neighbors(self, poi, level):
        nex = {}
        rv = []
        if poi[0] != self.maxy:
            nex.setdefault(self.y[poi[0] + 1][poi[1]], list()).append((poi[0] + 1, poi[1]))
        if poi[1] != self.maxx:
            nex.setdefault(self.y[poi[0]][poi[1] + 1], list()).append((poi[0], poi[1] + 1))
        if poi[0] != 0:
            nex.setdefault(self.y[poi[0] - 1][poi[1]], list()).append((poi[0] - 1, poi[1]))
        if poi[1] != 0:
            nex.setdefault(self.y[poi[0]][poi[1] - 1], list()).append((poi[0], poi[1] - 1))

        order = sorted(nex.keys())

        for j in order:
            for p in nex[j]:
                if (p not in self.visited and
                    (p not in self.point_costs or self.point_costs[p] >= level + j)):
                    rv.append(p)

        return rv

gri = grid()

with open(sys.argv[1], 'r') as f:
    for i in f.readlines():
        gri.addline(i.strip())
gri.largegrid()
#for f in gri.y:
#    print("".join(map(str, f)))

gri.findpath()

print(gri.current_smallest_solution_level)