char* addBinary(char* a, char* b) 
{
    int la = strlen(a);
    int lb = strlen(b);
    int lr = la > lb ? la : lb;
    int carry = 0;
    /*可能存在进位，计算前无法预判，多申请进位和\0*/
    char *res = (char*)calloc(lr + 2, sizeof(char));
    res[lr + 1] = '\0';
    /*指向a b 最后一个数值*/
    la--; lb--;
    while (la >= 0 || lb >= 0) 
    {
        int ba = la >= 0 ? a[la--] - '0' : 0;
        int bb = lb >= 0 ? b[lb--] - '0' : 0;
        int br = ba ^ bb ^ carry;
        carry = (ba + bb + carry > 1) ? 1 : 0;
      //carry = (ba & bb) | (carry & (ba ^ bb));

        res[lr--] = br + '0';
    }
    
    /*无进位，返回res + 1*/
    if (!carry) 
        return res + 1;
    
    /*有进位置res[0]为1*/
    res[0] = '1';
    return res;
}