#!/usr/bin/env python3
''' reveal the connected zeros of a minesweeper board
    board is 1-indexed and square '''

def is_onboard(c):
    (a,b) = c
    return a >= 1 and b >= 1 and a <= BOARD and b <= BOARD

def adjacents(c):
    (a,b) = c
    adjs = [ (a+x, b+y) for x in range(-1,2) for y in range(-1,2) ]
    return [ x for x in adjs if is_onboard(x) ]

def mine_count(c):
    return len([ x for x in adjacents(c) if x in MINES ])

def ls_zeros(unvisited, visited):
    unvisited = [ x for x in unvisited if x not in visited and mine_count(x) == 0 ]
    if unvisited == []:
        return sorted(visited)
    hd, *tl = unvisited
    return ls_zeros(tl + adjacents(hd), visited + [hd])


BOARD = 3
MINES = [ (1,1) ]
assert ls_zeros([(1,1)], []) == []
assert ls_zeros([(2,1)], []) == []
assert ls_zeros([(1,3)], []) == [(1, 3), (2, 3), (3, 1), (3, 2), (3, 3)]

MINES = [ (1,1), (3,1) ]
assert ls_zeros([(1,3)], []) == [(1, 3), (2, 3), (3, 3)]
assert ls_zeros([(2,3)], []) == [(1, 3), (2, 3), (3, 3)]

BOARD = 5
MINES = [ (1,3), (2,3), (3,3), (4,3), (5,3) ]
assert ls_zeros([(5,5)], []) == [(1, 5), (2, 5), (3, 5), (4, 5), (5, 5)]