LeetCode#67 Add Binary

Problem Definition:

Given two binary strings, return their sum (also a binary string).

For example,
a = "11"
b = "1"
Return "100".

 

Solution: crack it in a Pythonista way:

def addBinary(a, b):
    a=int(a,2)
    b=int(b,2)
    return bin(a+b)[2:]

 

Now let's recall something called full adder. And by simulating it, we get another solution, trivial though.

def addBinary(self,a, b):
        if a==None or a=='':
            return b
        if b==None or b=='':
            return a
        ia,ib=len(a)-1,len(b)-1
        ba,bb,c=[0]*3
        s=''
        while ia>=0 or ib>=0 or c==1:
            ba=ord(a[ia])-ord('0') if ia>=0 else 0
            bb=ord(b[ib])-ord('0') if ib>=0 else 0
            ia-=1
            ib-=1
            r=ba^bb^c #xor
            c=1 if ba+bb+c>=2 else 0
            s+=str(r)
        return s[::-1]