Merge K Sorted LinkedLists

Author: rahuldev8

Programs/MergeKsortedLists.java

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+//Contributed by Dev jr - https://github.com/Dev-jr-8 
+
+class Solution
+{
+ //Function to merge K sorted linked list.
+ //Logic for merging two sorted linked list
+ Node mergetwolist(Node head1, Node head2)
+ {
+ Node a = head1;
+ Node b = head2;
+ Node head = null;
+ Node tail = null;
+ 
+ if(a==null)return b;
+ if(b==null)return a;
+ 
+ if(a.data<b.data)
+ {
+ head = a;
+ tail = a;
+ a = a.next;
+ }
+ else
+ {
+ head = b;
+ tail = b;
+ b = b.next;
+ }
+ 
+ while(a!=null && b!=null)
+ {
+ if(a.data<b.data)
+ {
+ tail.next = a;
+ tail = a;
+ a = a.next;
+ }
+ else
+ {
+ tail.next = b;
+ tail = b;
+ b = b.next;
+ }
+ }
+ if(a==null)tail.next=b;
+ if(b==null)tail.next=a;
+ 
+ return head;
+ } 
+ 
+ Node mergeKList(Node[]arr,int K)
+ {
+ //Add your code here.
+ Node ans = null;
+ //Taking pair of sorted linked list and merging them, Storing their start point(head)
+ //in ans reference variable
+ for(Node i : arr)
+ {
+ ans = mergetwolist(i,ans);
+ }
+ return ans;
+ }
+ //Time Complexity : o(n^2)
+ //Space Complexity : o(1)
+}
+
+//geeksforgeeks driver code
+
+//{ Driver Code Starts
+ import java.util.*;
+
+ class Node
+ {
+ int data;
+ Node next;
+ 
+ Node(int key)
+ {
+ data = key;
+ next = null;
+ }
+ }
+ 
+ 
+ class GfG
+ {
+ public static void printList(Node node)
+ {
+ while(node != null)
+ {
+ System.out.print(node.data + " ");
+ node = node.next;
+ }
+ }
+ 
+ public static void main (String[] args) {
+ Scanner sc = new Scanner(System.in);
+ 
+ int t = sc.nextInt();
+ while(t-- > 0)
+ { 
+ int N = sc.nextInt();
+ 
+ Node []a = new Node[N];
+ 
+ for(int i = 0; i < N; i++)
+ {
+ int n = sc.nextInt();
+ 
+ Node head = new Node(sc.nextInt());
+ Node tail = head;
+ 
+ for(int j=0; j<n-1; j++)
+ {
+ tail.next = new Node(sc.nextInt());
+ tail = tail.next;
+ }
+ 
+ a[i] = head;
+ }
+ 
+ Solution g = new Solution();
+ 
+ Node res = g.mergeKList(a,N);
+ if(res!=null)
+ printList(res);
+ System.out.println();
+ }
+ }
+ }