Implement Priority Queue via Linked List in C++

Introduction:

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Working Principle:

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Example:

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Code:

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// C++ code to implement Priority Queue
// using Linked List
#include <bits/stdc++.h>
using namespace std;

// Node
typedef struct node
{
	int data;

	// Lower values indicate
	// higher priority
	int priority;

	struct node* next;

} Node;

// Function to create a new node
Node* newNode(int d, int p)
{
	Node* temp = (Node*)malloc(sizeof(Node));
	temp->data = d;
	temp->priority = p;
	temp->next = NULL;

	return temp;
}

// Return the value at head
int peek(Node** head)
{
	return (*head)->data;
}

// Removes the element with the
// highest priority form the list
void pop(Node** head)
{
	Node* temp = *head;
	(*head) = (*head)->next;
	free(temp);
}

// Function to push according to priority
void push(Node** head, int d, int p)
{
	Node* start = (*head);

	// Create new Node
	Node* temp = newNode(d, p);

	// Special Case: The head of list has
	// lesser priority than new node. So
	// insert newnode before head node
	// and change head node.
	if ((*head)->priority > p)
	{
		
		// Insert New Node before head
		temp->next = *head;
		(*head) = temp;
	}
	else
	{
		
		// Traverse the list and find a
		// position to insert new node
		while (start->next != NULL &&
			start->next->priority < p)
		{
			start = start->next;
		}

		// Either at the ends of the list
		// or at required position
		temp->next = start->next;
		start->next = temp;
	}
}

// Function to check is list is empty
int isEmpty(Node** head)
{
	return (*head) == NULL;
}

// Driver code
int main()
{
	
	// Create a Priority Queue
	// 7->4->5->6
	Node* pq = newNode(4, 1);
	push(&pq, 5, 2);
	push(&pq, 6, 3);
	push(&pq, 7, 0);

	while (!isEmpty(&pq))
	{
		cout << " " << peek(&pq);
		pop(&pq);
	}
	return 0;
}

Output:

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