Javascript Program To Merge K Sorted Linked Lists Using Min Heap - Set 2

// Javascript implementation to merge
// k sorted linked lists using MIN HEAP method
class Node {
    constructor(data) {
        this.data = data;
        this.next = null;
    }
}

// Function to merge k sorted 
// linked lists
function mergeKSortedLists(arr, k) {
    let head = null, last = null;

    // priority_queue 'pq' implemeted
    // as min heap with the help of 
    // 'compare' function
    let pq = [];

    // Push the head nodes of all
    // the k lists in 'pq'
    for (let i = 0; i < k; i++)
        if (arr[i] != null)
            pq.push(arr[i]);

    pq.sort(function (a, b) {
        return a.data - b.data;
    });

    // loop till 'pq' is not empty
    while (pq.length != 0) {
        // Get the top element of 'pq'
        let top = pq[0];
        pq.shift();

        // Check if there is a node next 
        // to the 'top' node in the list 
        // of which 'top' node is a member
        if (top.next != null)

            // Push the next node in 'pq'
            pq.push(top.next);

        // if final merged list is empty
        if (head == null) {
            head = top;

            // Points to the last node so far 
            // of the final merged list
            last = top;
        }
        else {
            // Insert 'top' at the end of the 
            // merged list so far
            last.next = top;

            // Update the 'last' pointer
            last = top;
        }
        pq.sort(function (a, b) { return a.data - b.data; });
    }
    // Head node of the required merged list
    return head;
}

// Function to print the singly linked list
function printList(head) {
    while (head != null) {
        console.log(head.data);
        head = head.next;
    }
}

// Utility function to create a 
// new node
function push(data) {
    let newNode = new Node(data);
    newNode.next = null;
    return newNode;
}

// Driver code
// Number of linked lists
let k = 3;

// Number of elements in each list
let n = 4;

// An array of pointers storing the 
// head nodes of the linked lists
let arr = new Array(k);

arr[0] = new Node(1);
arr[0].next = new Node(3);
arr[0].next.next = new Node(5);
arr[0].next.next.next = new Node(7);

arr[1] = new Node(2);
arr[1].next = new Node(4);
arr[1].next.next = new Node(6);
arr[1].next.next.next = new Node(8);

arr[2] = new Node(0);
arr[2].next = new Node(9);
arr[2].next.next = new Node(10);
arr[2].next.next.next = new Node(11);

// Merge all lists
let head = mergeKSortedLists(arr, k);
printList(head);

// This code is contributed by avanitrachhadiya2155