adventofcode2022/day12/sol.py

import heapq
import string

elevation = {c:i for i, c in enumerate(string.ascii_lowercase)}
elevation['E'] = elevation['z']
elevation['S'] = elevation['a']

data = open("input").read().splitlines(False)
#print(*data, sep="\n")

extra = []
for y, row in enumerate(data):
    for x, c in enumerate(row):
        if c == 'S':
            start = (x,y)
        elif c == 'E':
            goal = (x,y)
        elif c == 'a':
            # for part 2
            extra.append((x,y))

def get(x, y):
    return elevation[data[y][x]]

def solve(part):
    q = [(0, start)]

    if part == 2:
        q.extend((0,p) for p in extra)

    done = {}
    while q:
        cost, (x,y) = heapq.heappop(q)
        if (x,y) in done:
            continue
        #print(x,y,cost)
        if (x,y) == goal:
            print('found', cost)
            break
        here = get(x,y)
        done[(x,y)] = cost

        def push(x,y):
            if 0 <= y < len(data):
                if 0 <= x < len(data[y]):
                    if get(x,y) <= here+1 and (x,y) not in done:
                        heapq.heappush(q, (cost+1, (x,y)))
        push(x-1, y)
        push(x+1,y)
        push(x, y-1)
        push(x, y+1)

solve(1)
solve(2)