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  1. #include <iostream>
  2. #include <string>
  3.  
  4. using namespace std;
  5.  
  6. template<typename T>
  7. struct Node
  8. {
  9.         Node *Next;
  10.         Node *Prev;
  11.         T val;
  12. };
  13.  
  14. template<typename T>
  15. class queue
  16. {
  17.         Node<T> *Last;
  18.         Node<T> *First;
  19.         int size;
  20.  
  21. public:
  22.         queue();
  23.         ~queue();
  24.         void push(T);
  25.         void pop();
  26.         void show_qF(std::ostream& stream);
  27.         void show_qL(std::ostream& stream);
  28.         bool empty();
  29.         int show_size();
  30. };
  31.  
  32. template<typename T>
  33. queue<T>::queue()
  34. {
  35.         Last = First = NULL;
  36.         size = 0;
  37. }
  38.  
  39. template<typename T>
  40. queue<T>::~queue()
  41. {
  42.         Node<T> *tmp;
  43.         while(Last != NULL)
  44.         {
  45.             tmp = Last -> Prev;
  46.             delete Last;
  47.             Last = tmp;
  48.         }
  49. }
  50.  
  51. template<typename T>
  52. void queue<T>::push(T n)
  53. {
  54.         Node<T> *p = new Node<T>;
  55.         p -> val = n;
  56.         p -> Next = First;
  57.         p -> Prev = NULL;
  58.         size++;
  59.  
  60.         if(First == NULL)
  61.         {
  62.             First = Last = p;
  63.             Last -> Next = NULL;
  64.             First -> Prev = NULL;
  65.             return;
  66.         }
  67.  
  68.         First -> Prev = p;
  69.         First = p;
  70. }
  71.  
  72. template<typename T>
  73. void queue<T>::pop()
  74. {
  75.         if(Last == NULL) return;
  76.  
  77.         Node<T> *tmp;
  78.         tmp = Last;
  79.         if(Last -> Prev != NULL)
  80.         {
  81.             Last = Last -> Prev;
  82.         }
  83.         else
  84.         {
  85.             Last = First = NULL;
  86.         }
  87.  
  88.         delete tmp;
  89.         size--;
  90. }
  91.  
  92. template<typename T>
  93. int queue<T>::show_size()
  94. {
  95.         return size;
  96. }
  97.  
  98. template<typename T>
  99. void queue<T>::show_qF(std::ostream& stream)
  100. {
  101.         Node<T> *p;
  102.         p = First;
  103.         while(p != NULL)
  104.         {
  105.             stream<< p -> val <<std::endl;
  106.             p = p -> Next;
  107.         }
  108. }
  109.  
  110. template<typename T>
  111. void queue<T>::show_qL(std::ostream& stream)
  112. {
  113.         Node<T> *p;
  114.         p = Last;
  115.         while(p != NULL)
  116.         {
  117.             stream<< p -> val <<std::endl;
  118.             p = p -> Prev;
  119.         }
  120. }
  121.  
  122. template<typename T>
  123. bool queue<T>::empty()
  124. {
  125.         return First == NULL;
  126. }
  127.  
  128.  
  129. int main() 
  130. {
  131.   queue<std::string> q;
  132.  
  133.   q.push("1");
  134.   q.push("2");
  135.   q.push("3");
  136.  
  137.   q.pop();
  138.  
  139.   q.show_qF(std::cout);
  140.   return 0;
  141. }
Runtime error #stdin #stdout 0s 15240KB
comments (?)
stdin
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Standard input is empty
stdout
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3
2
1
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https://ideone.com/eDUZHJ
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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