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  1. 	#include <iostream>
  2.  
  3. 	using std::cout;
  4. 	using std::endl;
  5.  
  6. 	class LinkedList
  7. 	{
  8. 	    struct Node
  9. 	    {
  10. 	        int x;
  11. 	        Node *next;
  12. 	    };
  13.  
  14. 	    Node *head;
  15.  
  16. 	    // get a pointer to the last node in the list.
  17. 	    // returns: head if the list is empty.
  18. 	    Node* last_node()
  19. 	    {
  20. 	    	Node* cur = head;
  21. 	    	while (cur->next)
  22. 	    		cur = cur->next;
  23. 	    	return cur;
  24. 	    }
  25.  
  26. 	public:
  27. 	    LinkedList()
  28. 	        : head(new Node { -1, nullptr })
  29. 	    {
  30. 	    }
  31.  
  32. 	    // If you absolutely have to have a constructor that adds a node:
  33. 	    LinkedList(int adds) : LinkedList()
  34. 	    {
  35. 	    	add(adds);
  36. 	    }
  37.  
  38. 	   	~LinkedList()  // destructor
  39. 	   	{
  40. 	   		// Free all of the nodes we created
  41. 	   		Node *next;
  42. 	   		for (Node* cur = head; cur != nullptr; cur = next) {
  43. 	   			next = cur->next;
  44. 	   			delete cur;
  45. 	   		}
  46. 	   	}
  47.  
  48. 	    void add(int adds)
  49. 	    {
  50. 	    	Node* tail = last_node();
  51. 	        tail->next = new Node { adds, nullptr };
  52. 	        cout << "added:  " << tail->next->x << endl;
  53. 	    }
  54.  
  55. 		bool empty() const
  56. 		{
  57. 			return (head->next == nullptr);
  58. 		}
  59.  
  60. 	    // returns: value of the last node (-1 if list is empty)
  61. 	    int back()
  62. 	    {
  63. 	    	return last_node()->x;
  64. 	    }
  65.  
  66.  
  67. 	  	// Normal implementation requires caller to check !empty() first:
  68.  
  69. 	    // returns: value of the first non-head node
  70. 	    // if the list is empty, undefined behavior.
  71. 	    int front()
  72. 	    {
  73. 			return head->next->x;
  74. 	    }
  75.  
  76. 		// alternatively:
  77.  
  78. 		// returns: value of the first non-head node or -1 if the list is empty.
  79. 		int front_safe()
  80. 		{
  81. 	    	return (head->next) ? head->next->x : head->x;
  82. 		}
  83. 	};
  84.  
  85. 	int main()
  86. 	{
  87. 	  LinkedList lt;
  88. 	  lt.add(1);
  89. 	  lt.add(2);
  90. 	  lt.add(3);
  91. 	  lt.add(4);
  92. 	  cout << lt.front() << endl;
  93. 	  cout << lt.back() << endl;
  94. 	}
  95.  
Success #stdin #stdout 0s 3456KB
comments (?)
stdin 
Standard input is empty
stdout 
added:  1
added:  2
added:  3
added:  4
1
4
https://ideone.com/UzYCii
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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