1 #include 
      
        2 #include 
       
         3 using namespace std; 4  5 class QueuebyStack 6 { 7 public: 8     void enqueue(char ch) 9     {10         s1.push(ch);11     }12     void dequeue()13     {14         if(s2.empty())15         {16             while(!s1.empty())17             {18                 char temp = s1.top();19                 s2.push(temp);20                 s1.pop();21             }22         }23         s2.pop();24     }25     bool empty()26     {27         return s1.empty()&&s2.empty();28     }29     char front()30     {31         if(s2.empty())32         {33             while(!s1.empty())34             {35                 char temp = s1.top();36                 s2.push(temp);37                 s1.pop();38             }39         }40         return s2.top();41     }42     long size() const43     {44         return s1.size()+s2.size();45     }46 private:47     stack
        
          s1;48     stack
         
           s2;49 };50 51 int main()52 {53     QueuebyStack q;54     char ch;55     while(cin>>ch&&ch != '0')56     {57         q.enqueue(ch);58     }59     while(!q.empty())60     {61         cout<
          
           <<" ";62         q.dequeue();63     }64     cout<