class Solution {public:    string addBinary(string a, string b) {        string longer=a.length()>b.length() ? a:b;        string shorter=a.length()>b.length() ? b:a;        int add=0;        int j=longer.length()-1;        for(int i=shorter.length()-1;i>=0;--i,--j){            if(shorter[i]-‘0‘+longer[j]-‘0‘+add>1){                longer[j]=‘0‘+(shorter[i]-‘0‘+longer[j]-‘0‘+add)%2;                add=1;            }else{                longer[j]=‘0‘+(shorter[i]-‘0‘+longer[j]-‘0‘+add)%2;                add=0;            }        }        while(j>=0){            if(longer[j]-‘0‘+add>1){                longer[j]=‘0‘;                add=1;            }else{                longer[j]=longer[j]+add;                add=0;            }            --j;        }        if(add)            longer.insert(0,1,‘1‘);        return longer;    }};