Day 12 solution without queues for Advent of Code 2022 at https://adventofcode.com/2022/day/12

day12.py

g = []
for line in open('day12.input'):
    g.append([ord(c) for c in line.strip()])
n = len(g)
# find S and E and transform to ord('a') and ord('z')
s, e = None, None
for i in range(n):
    for j in range(len(g[i])):
        if g[i][j] == ord('S'):
            g[i][j] = ord('a')
            s = (i, j)
        elif g[i][j] == ord('E'):
            g[i][j] = ord('z')
            e = (i, j)

def sp(s, ascent=True): # shortest path to all
    x, y = s
    d = [[1e9 for _ in range(len(g[i]))] for i in range(n)]
    d[x][y] = 0
    ch = True
    while ch:
        ch = False
        for i in range(n):
            for j in range(len(g[i])):
                if d[i][j] == 1e9: continue
                for dx, dy in ((0, 1), (0, -1), (1, 0), (-1, 0)):
                    ni, nj = i + dx, j + dy
                    if ni < 0 or ni >= n or nj < 0 or nj >= len(g[i]): continue
                    if ascent and g[ni][nj] - g[i][j] > 1: continue
                    if not ascent and g[i][j] - g[ni][nj] > 1: continue
                    if d[ni][nj] > d[i][j] + 1:
                        d[ni][nj] = d[i][j] + 1
                        ch = True
    return d

print("Part 1:", sp(s)[e[0]][e[1]])

d = sp(e, ascent=False)
mn = 1e9
for i in range(n):
    for j in range(n):
        if g[i][j] == ord('a'):
            mn = min(mn, d[i][j])

print("Part 2:", mn)