1 class Solution { 2 public: 3     char addBit(char a,char b,char &c) 4     { 5         if(a==b&&a==‘1‘) 6         { 7             char ret; 8             ret=c; 9             c=‘1‘;10             return ret;11         }12         else if(a==b&&a==‘0‘)13         {14             15             if(c==‘0‘)16             {17                 return ‘0‘;18             }19             else20             {21                 c=‘0‘;22                 return ‘1‘;23             }24         }25         else26         {27             if(c==‘1‘)28                return ‘0‘;29             else30                return ‘1‘;31             32         }33     }34     35     string addBinary(string a, string b) {36         37         int na=a.length()-1;38         int nb=b.length()-1;39         40         if(na!=nb)41         {42             string tmp(abs(na-nb),‘0‘);43             if(na>nb)44                 b=tmp+b;45             else46                 a=tmp+a;47         }48         49         int i=a.length()-1;50         string result(a.length(), ‘1‘);51         char c=‘0‘;52         53         while(i>=0)54         {55             result[i]=addBit(a[i],b[i],c);56             i--;57         }58         if(c==‘0‘)59         {60             return result;61         }62         else63         {64             return ‘1‘+result;65         }66     }67 };