【剑指offer 面试题7】用两个栈实现队列

 #include <iostream>
 #include <stack>
 using namespace std;

 template <typename T> class SQueue
 {
 public:
     SQueue():cnt(){};

     void push(const T& node);
     T pop();
     int getSize();

 private:
     stack<T> pushstack;
     stack<T> popstack;

     int cnt;
 };

 template <typename T> void SQueue<T>::push(const T& node)
 {
     pushstack.push(node);

     cnt++;
 }

 template <typename T> T SQueue<T>::pop()
 {
     if(popstack.empty())
     {
         while(!pushstack.empty())
         {
             T tmp = pushstack.top();
             pushstack.pop();
             popstack.push(tmp);
         }
     }

     if(popstack.empty())
     {
         throw new exception();
     }

     T ret = popstack.top();
     popstack.pop();

     cnt--;

     return ret;
 }

 template <typename T> int SQueue<T>::getSize()
 {
     return cnt;
 }

 int main()
 {
     SQueue<int> Queue;
     Queue.push();
     Queue.push();
     Queue.push();

     cout<<"currnet size:"<<Queue.getSize()<<endl;

     cout<<Queue.pop()<<endl;

     cout<<"currnet size:"<<Queue.getSize()<<endl;

     cout<<Queue.pop()<<endl;
     cout<<Queue.pop()<<endl;
 }