leetcode 67 Add Binary

class Solution {
public:
    string addBinary(string a, string b) 
    {
        
        string result = "";
        int c = 0;
        int i = a.size() - 1;
        int j = b.size() - 1;
        
        while(i >= 0 || j >=0 ||c ==1)
        {
            c += i >= 0 ? a[i--] - '0':0;
            c += j >= 0 ? b[j--] - '0':0;
            result = char( c% 2 + '0') + result;
            c /= 2;
            
        }
        
        return result;
        
        
    }
};

char* addBinary(char* a, char* b) {
    int n, m;
    for (n=0; *a; a++, n++) ;
    for (m=0; *b; b++, m++) ;
    char *p = (char*)malloc(m>n ? m+2 : n+2), *last = p;
    int c = 0;
    while (n || m || c) {
        int s = c;
        if (n) {
            s += *(--a)-'0';
            --n;
        }
        if (m) {
            s += *(--b)-'0';
            --m;
        }
        *last++ = (s&1)+'0';
        c = s>>1;
    }
    *last=0;
    char *start = p, t;
    while (start+1 < last) { // reverse string
        t = *start;
        *start++=*(--last);
        *last=t;
    }
    return p;
}

class Solution:
    # @param {string} a
    # @param {string} b
    # @return {string}
    def addBinary(self, a, b):
        i, m, n, result, carry = 1, len(a), len(b), [], 0
        while i <= m or i <= n:
            temp = carry
            if i <= m:
                temp += int(a[-i])
            if i <= n:
                temp += int(b[-i])

            carry = temp / 2
            result.append(str(temp % 2))
            i += 1

        if carry:
            result.append(str(carry))

        return ''.join(result[::-1])

or a really short one if you want

class Solution:
    # @param {string} a
    # @param {string} b
    # @return {string}
    def addBinary(self, a, b):
        return '{0:b}'.format(int(a, 2) + int(b, 2))


class Solution:
    # @param {string} a
    # @param {string} b
    # @return {string}
    def addBinary(self, a, b):
        return bin(int(a,2) + int(b,2))[2:]