var count = CountZero(board);//数一数一共几个空格
var pos = ~~(Math.random() * count)
var flag = 0
for (i = 0; i < 4; i++) {
for (j = 0; j < 4; j++) {
if (board[i][j] == 0) {
if (pos == 0) {
flag = 1;
break; //跳出循环时board[i][j]就是随机出来的位置
}
pos--;
}
}
if (flag == 1)
break;
}
