1、10進制轉2進制
def tansform(num):
s=[]
if num<0:
return "-"+transform(abs(num)))
while True:
num,remainder=divod(num,2)#divod(a,b),輸出(a//b,a%b)即整數和餘數
s.append(remainder)
if num==0:
return "",join(s[::-1])