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BFS solution in Clear category for Express Delivery by lightholy
from heapq import *
def checkio(field):
h = []
heappush(h, [0, True, 0, 0, ''])
v = set()
while True:
t, b, r, c, s = heappop(h)
if r < 0 or r >= len(field) or c < 0 or c >= len(field[r]):
continue
if field[r][c] == 'W' or (b, r, c) in v:
continue
if field[r][c] == 'E' and b:
return s
v.add((b, r, c))
if field[r][c] == 'B':
heappush(h, [t + 1, not b, r, c, s + 'B'])
for dr, dc, ds in [[0, -1, 'L'], [0, 1, 'R'], [1, 0, 'D'], [-1, 0, 'U']]:
heappush(h, [t + 1 + int(b), b, r + dr, c + dc, s + ds])
May 4, 2014
