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  1. /*Implementation of "queue" with basic operations using LINKED LIST */
  2. #include<iostream>
  3. using namespace std;
  4.  
  5. struct node{
  6.     int val;
  7.     node *next;
  8. }*head=NULL, *tail=NULL;
  9.  
  10.  
  11. void ENQUE(int key);        // ~insertion
  12. int  DEQUEUE();            // ~deletion
  13. void TRAVERSE();
  14. bool isEmpty();
  15.                           // a q implemented using linked list can never be full theoretically
  16. int main(){
  17.     int ch,key;
  18.     do{
  19.         cout<<"1. Insertion\n2. Deletion\n3. Traverse\n4. Exit\n";
  20.         cout<<"Enter your choice : ";
  21.         cin>>ch;
  22.         switch(ch){
  23.             case 1 : cout<<"Enter the value to be inserted :";
  24.                     cin>>key;
  25.                     ENQUE(key);
  26.                     TRAVERSE();
  27.                     break;
  28.             case 2 : if(!isEmpty()){
  29.                         cout<<DEQUEUE()<<" deleted successfully.\n";
  30.                         TRAVERSE();
  31.                     }
  32.                     else
  33.                         cout<<"Empty Queue !!!\n";
  34.                     break;
  35.             case 3 : TRAVERSE();
  36.                     break;
  37.             case 4 :cout<<"Exiting..."; 
  38.                     break;
  39.             default: cout<<"Invalid choice. Please try again..";
  40.         }
  41.     }while(ch!=4);
  42.     return 0;
  43. }
  44.  
  45. void ENQUE(int x){
  46.     if(tail==NULL){
  47.         tail = new node();
  48.         tail->val =x;
  49.         tail->next=NULL;
  50.         head=tail;
  51.     }
  52.     else{
  53.         tail->next = new node();
  54.         tail = tail->next;
  55.         tail->val =x;
  56.         tail->next=NULL;
  57.     }
  58. }
  59.  
  60. int  DEQUEUE(){
  61.     node *temp = head;
  62.     int item =head->val;
  63.  
  64.     head = head->next;
  65.     delete(temp);
  66.  
  67.     if(head==NULL)
  68.         tail=NULL;
  69.     return item;
  70. }
  71.  
  72. void TRAVERSE(){
  73.     if(!isEmpty()){
  74.         node *ptr = head;
  75.         cout<<"\nhead";
  76.         while(ptr){
  77.  
  78.             cout<<" -> "<<ptr->val;
  79.             ptr=ptr->next;
  80.         }
  81.         cout<<" <- tail\n";
  82.         cout<<endl;
  83.     }
  84.     else
  85.         cout<<"Empty Queue !!!\n";
  86. }
  87.  
  88. bool isEmpty(){
  89.     if(tail==NULL && head==NULL)
  90.         return true;
  91.     else
  92.         return false;
  93. }
  94.  
Success #stdin #stdout 0s 2992KB
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stdin
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stdout
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1. Insertion
2. Deletion
3. Traverse
4. Exit
Enter your choice : Enter the value to be inserted :
head -> 1 <- tail

1. Insertion
2. Deletion
3. Traverse
4. Exit
Enter your choice : Enter the value to be inserted :
head -> 1 -> 2 <- tail

1. Insertion
2. Deletion
3. Traverse
4. Exit
Enter your choice : Enter the value to be inserted :
head -> 1 -> 2 -> 3 <- tail

1. Insertion
2. Deletion
3. Traverse
4. Exit
Enter your choice : 1 deleted successfully.

head -> 2 -> 3 <- tail

1. Insertion
2. Deletion
3. Traverse
4. Exit
Enter your choice : 2 deleted successfully.

head -> 3 <- tail

1. Insertion
2. Deletion
3. Traverse
4. Exit
Enter your choice : Exiting...
https://ideone.com/vtRphX
Q - Linked List Based
language:
C++ (gcc 8.3)
created:
10 years ago
visibility:
public

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