102 lines
2.3 KiB
C++
102 lines
2.3 KiB
C++
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// Content: Queue using linked list (FIFO)
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// Author: Tawfik Yasser
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// Date: Fri, 5 Mar 2021
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#include <iostream>
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using namespace std;
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// Class `Node` to represent every item in the queue
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class Node
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{
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public:
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int data; // Item data
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Node *next; // Pointer to next item
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Node() {} // Empty constructor
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};
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// Claas to represent the queue using linked list
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class QueueLL
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{
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private:
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Node *front; // Pointer to the head of the queue
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Node *rear; // Pointer to the end of the queue
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int _length;
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public:
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QueueLL() //Empty constructor to initialize front and rear to NULL because in the start the queue will be empty
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{
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front = rear = NULL;
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_length = 0 ;
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}
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// Function `Enqueue` to add new item to the queue from the rear side (End)
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void enqueue(int value)
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{
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Node *newNode = new Node();
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newNode->data = value;
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newNode->next = NULL;
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if(front == NULL && rear == NULL) // Empty queue
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{
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front = rear = newNode;
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}
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else
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{
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rear->next = newNode;
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rear = newNode;
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}
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_length++;
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}
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// Function `Dequeue` to remove an item from the queue from the front side (Start)
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void dequeue()
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{
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Node *temp = front;
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front = front->next;
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delete temp; //Free the memory
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_length--;
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}
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// Function `Peek` to return the first item in the queue
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void peek()
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{
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cout<<front->data<<endl;
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}
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// Function `Print` to display the items of the queue
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void print()
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{
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if(front == NULL && rear == NULL) //Empty queue
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{
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cout<<"Empty Queue"<<endl;
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}
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else
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{
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Node *temp = front;
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while(temp != NULL) // Till the end of the queue
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{
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cout<<"[ "<<temp->data<<" ] ";
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temp = temp->next;
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}
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}
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}
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int _size()
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{
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return _length;
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}
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};
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int main()
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{
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//Test the functions
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QueueLL qll;
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qll.enqueue(5);
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qll.enqueue(3);
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qll.enqueue(-2);
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qll.print();
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cout<<endl;
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qll.peek();
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cout<<"Queue size = "<<qll._size()<<endl;
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qll.dequeue();
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qll.print();
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cout<<endl;
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qll.peek();
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cout<<"Queue size = "<<qll._size()<<endl;
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return 0;
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}
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