二进制相加

string addBinary(string a,string b) {
        int carry=0;
        int n=a.size()>b.size()?a.size():b.size();    //最长的那个
        reverse(a.begin(),a.end());
        reverse(b.begin(),b.end());
        string sum;
       for(size_t i=0;i<n;++i)
       {
           int ai,bi,val;
           
           ai=(i<a.size()?a[i]-‘0‘: 0);
           bi=(i<b.size()?b[i]-‘0‘: 0);                   
           
           val=(ai+bi+carry)%2;
           carry=(ai+bi+carry)/2;
           
           sum.insert(sum.begin(),val+‘0‘);
       }
        if(carry==1)
            sum.insert(sum.begin(),‘1‘);
        return sum;
        
    }