import itertools
def safe_pawns(pawns):
safe_squares = itertools.chain(*[calc_safe_squares(p) for p in pawns])
return len(pawns & set(safe_squares))
def calc_safe_squares(pos):
return (chr(ord(pos[0]) - 1) + str(int(pos[1]) + 1),
chr(ord(pos[0]) + 1) + str(int(pos[1]) + 1))
if __name__ == '__main__':
#These "asserts" using only for self-checking and not necessary for auto-testing
assert safe_pawns({"b4", "d4", "f4", "c3", "e3", "g5", "d2"}) == 6
assert safe_pawns({"b4", "c4", "d4", "e4", "f4", "g4", "e5"}) == 1
http://www.checkio.org/mission/pawn-brotherhood/