队列入队总出现Segmentation fault，不知道这段代码该怎么改

Question

#include  <iostream>
using  namespace  std;

template  <class  DataType>
struct  node{
        DataType  data;
        node<DataType>*  next;
};

template  <class  DataType>
class  cirLinkQueue{
public:
        cirLinkQueue();
        cirLinkQueue(DataType  a[],int  n);
        void  enQueue(DataType  elem);
        bool  deQueue();
        void  printQueue();
private:
        node<DataType>*  rear;
};

template  <class  DataType>
cirLinkQueue<DataType>::cirLinkQueue()
{
        rear  =  NULL;
}

template  <class  DataType>
cirLinkQueue<DataType>::cirLinkQueue(DataType  a[],int  n)
{
        if(n  ==  1){
                rear  =  new  node<DataType>;
                rear->data  =  a[0];
                rear->next  =  rear;
        }
        else{
                rear  =  new  node<DataType>;
                rear->data  =  a[0];
                rear->next  =  rear;
                for(int  i=1;i<n;++i){
                        node<DataType>*  s  =  new  node<DataType>;
                        s->data  =  a[i];
                        s->next  =  rear->next;
                        rear->next  =  s;
                        rear  =  s;
                }
        }
}

template  <class  DataType>
void  cirLinkQueue<DataType>::enQueue(DataType  elem)
{
     node<DataType> *s = NULL;
     s = new node<DataType>;
     s->data=elem;
     s->next=rear->next;
     rear->next=s;
     rear=s;

}

template  <class  DataType>
bool  cirLinkQueue<DataType>::deQueue()
{
      DataType x;
      node<DataType> *p=NULL;
      if(rear ==rear->next) throw"下溢";
      p = rear->next->next;
      x=p->data;
      rear->next->next=p->next;
      if(p==rear)rear = rear->next;
      delete p ;
      return x;
}

template  <class  DataType>
void  cirLinkQueue<DataType>::printQueue()
{
        if(rear  ==  NULL)
                cout<<"Empty"<<endl;
        else{
                node<DataType>*  p  =  rear->next;
                while(p  !=  rear){
                        cout<<p->data<<"  ";
                        p  =  p->next;
                }
                cout<<p->data<<endl;
        }
}
int  main()
{
        cirLinkQueue<int>  Q;
        int  m,n;
        cin>>m;
        while(m--){
                int  elem;
                cin>>elem;
                Q.enQueue(elem);
        }
        cin>>n;
        while(n--){
                bool  res  =  Q.deQueue();
                if(!res)  break;
        }
        Q.printQueue();
        return  0;
}

Answer 1

使用默认构造函数的时候，rear没有初始化，后面访问肯定段错误撒