프로그래머스_안전지대 (그래프)

def solution(board):
    cnt = 0
    dx=[-1,1,0,0,-1,-1,1,1]
    dy=[0,0,-1,1,-1,1,-1,1]
    visited=[[False]*len(board[0]) for _ in range(len(board))]
    for x in range(len(board)):
        for y in range(len(board[0])):
            if board[x][y]==1:
                cnt+=1
                for i in range(8):
                    nx=x+dx[i]
                    ny=y+dy[i]
                    if nx<0 or ny<0 or nx>=len(board) or ny>=len(board[0]):
                        continue
                    if board[nx][ny]==0 and not visited[nx][ny]:
                        visited[nx][ny]=True
                        cnt+=1
    return len(board)*len(board[0])-cnt