题目

给你两个二进制字符串，返回他们的和（用二进制表示）。

代码

```def addBinary(a,b):
if len(a) < len(b):
    a,b = b,a
a = a[::-1]
b = b[::-1]
b += (len(a)-len(b))*'0'
cin = 0
c = []
for i in range(len(a)):
    aList = [a[i],b[i],cin]
    if aList.count('1') == 1 or aList.count('1') == 3:
        c.append('1')
    else:
        c.append('0')
    if aList.count('1') > 1:
        cin = '1'
    else:
        cin = '0'
if cin == '1':
        c.append('1')
return ''.join(c[::-1])

print(addBinary('11', '1101'))