Given a Linked List and a key K. The task is to write a program to delete all the nodes from the list that are lesser than the key K.
Examples:
Input :12->15->9->11->5->6 K = 9 Output : 12 -> 15 -> 9 -> 11 Input : 13->4->16->9->22->45->5->16->6 K = 10 Output : 13 -> 16 -> 22 -> 45 -> 16
Approach: The approach is similar to deleting all nodes from the list which are greater than the given key.
There are two possible cases:
- Head node holds a value less than K: First check for all occurrences at head node which are lesser than ‘K’, delete them and change the head node appropriately.
- Some intermediate node holds value less than k: Start traversing from head and check if current node’s value is less than K. If yes then delete that node and move forward in the list.
Below is the implementation of the above approach:
CPP
// C++ program to delete all the nodes from the list // that are lesser than the specified value K #include <bits/stdc++.h> using namespace std;
// structure of a node struct Node {
int data;
Node* next;
}; // function to get a new node Node* getNode( int data)
{ Node* newNode = new Node;
newNode->data = data;
newNode->next = NULL;
return newNode;
} // function to delete all the nodes from the list // that are lesser than the specified value K void deleteLesserNodes(Node** head_ref, int K)
{ Node *temp = *head_ref, *prev;
// If head node itself holds the value lesser than 'K'
while (temp != NULL && temp->data < K) {
*head_ref = temp->next; // Changed head
free (temp); // free old head
temp = *head_ref; // Change temp
}
// Delete occurrences other than head
while (temp != NULL) {
// Search for the node to be deleted,
// keep track of the previous node as we
// need to change 'prev->next'
while (temp != NULL && temp->data >= K) {
prev = temp;
temp = temp->next;
}
// If required value node was not present
// in linked list
if (temp == NULL)
return ;
// Unlink the node from linked list
prev->next = temp->next;
delete temp; // Free memory
// Update Temp for next iteration of
// outer loop
temp = prev->next;
}
} // function to a print a linked list void printList(Node* head)
{ while (head) {
cout << head->data << " " ;
head = head->next;
}
} // Driver code int main()
{ // Create list: 12->15->9->11->5->6
Node* head = getNode(12);
head->next = getNode(15);
head->next->next = getNode(9);
head->next->next->next = getNode(11);
head->next->next->next->next = getNode(5);
head->next->next->next->next->next = getNode(6);
int K = 9;
cout << "Initial List: " ;
printList(head);
deleteLesserNodes(&head, K);
cout << "\nFinal List: " ;
printList(head);
return 0;
} |
Java
/*package whatever //do not write package name here */ import java.io.*;
// Java program to delete all the nodes from the list // that are lesser than the specified value k // structure of a node class Node{
int data;
Node next;
public Node( int data){
this .data = data;
this .next = null ;
}
} public class GFG {
// function to delete all the nodes from the list
// that are lesser than the specified value k
public static Node deleteLesserNodes(Node head_ref, int K){
Node temp = head_ref;
Node prev = null ;
// If head node itself holds the value lesser than 'K'
while (temp != null && temp.data < K){
head_ref = temp.next; // changed head
temp = head_ref; // change temp
}
// Delete occurrences other than head
while (temp != null ){
// search for the node to be deleted,
// keep track of the previous node as we
// need to change 'prev->next'
while (temp != null && temp.data >= K){
prev = temp;
temp = temp.next;
}
// If required value nodes was not present
// in linked list
if (temp == null )
return head_ref;
// unlink the node from linked list
prev.next = temp.next;
// Update temp for next iteration of
// outer loop
temp = prev.next;
}
return head_ref;
}
// function to a print a linked list
public static void printList(Node head){
while (head != null ){
System.out.print(head.data + " " );
head = head.next;
}
}
// Driver code
public static void main(String[] args) {
Node head = new Node( 12 );
head.next = new Node( 15 );
head.next.next = new Node( 9 );
head.next.next.next = new Node( 11 );
head.next.next.next.next = new Node( 5 );
head.next.next.next.next.next = new Node( 6 );
int K = 9 ;
System.out.println( "Initial List:" );
printList(head);
head = deleteLesserNodes(head, K);
System.out.println( "\nFinal List:" );
printList(head);
}
} // The code is contributed by Arushi goel. |
Python3
# Python program to delete all the nodes from the list # that are lesser than the specified value K # structure of node class Node:
def __init__( self , key):
self .data = key
self . next = None
# function to get a new node def getNode(data):
return Node(data)
# function to delete all the nodes from the list # that are lesser than the specified value k def deleteLesserNodes(head_ref, K):
temp = head_ref
prev = None
# if head node itself holds the value lesser than 'K'
while (temp is not None and temp.data < K):
head_ref = temp. next #changed head
temp = head_ref # change temp
# delete occurrences other than head
while (temp is not None ):
# search for the node to be deleted
# keep track of the previous node as we
# need to change prev.next
while (temp is not None and temp.data > = K):
prev = temp
temp = temp. next
# if required value nodes was not present
# in linked list
if (temp is None ):
return head_ref
# unlink the node from linked list
prev. next = temp. next
# update temp for next iteration of
# outer loop
temp = prev. next return head_ref
# function to print a linked list def printList(head):
while (head is not None ):
print (head.data, end = " " )
head = head. next
print ( "\n" )
# driver code to test above functions head = getNode( 12 )
head. next = getNode( 15 )
head. next . next = getNode( 9 )
head. next . next . next = getNode( 11 )
head. next . next . next . next = getNode( 5 )
head. next . next . next . next . next = getNode( 6 )
K = 9
print ( "Initial List: " )
printList(head) head = deleteLesserNodes(head, K)
print ( "Final List: " )
printList(head) # THIS CODE IS CONTRIBUTED BY YASH AGARWAL(YASHAGARWAL2852002) |
C#
using System;
// structure of a node class Node
{ public int data;
public Node next;
public Node( int data)
{
this .data = data;
next = null ;
}
} class LinkedList
{ // function to delete all the nodes from the list
// that are lesser than the specified value K
public static void DeleteLesserNodes( ref Node head_ref, int K)
{
Node temp = head_ref, prev = null ;
// If head node itself holds the value lesser than 'K'
while (temp != null && temp.data < K)
{
head_ref = temp.next; // Changed head
temp = head_ref; // Change temp
}
// Delete occurrences other than head
while (temp != null )
{
// Search for the node to be deleted,
// keep track of the previous node as we
// need to change 'prev.next'
while (temp != null && temp.data >= K)
{
prev = temp;
temp = temp.next;
}
// If required value node was not present
// in linked list
if (temp == null )
return ;
// Unlink the node from linked list
prev.next = temp.next;
// Free memory
temp = temp.next;
}
}
// function to a print a linked list
public static void PrintList(Node head)
{
while (head != null )
{
Console.Write(head.data + " " );
head = head.next;
}
}
// Driver code
public static void Main()
{
// Create list: 12->15->9->11->5->6
Node head = new Node(12);
head.next = new Node(15);
head.next.next = new Node(9);
head.next.next.next = new Node(11);
head.next.next.next.next = new Node(5);
head.next.next.next.next.next = new Node(6);
int K = 9;
Console.Write( "Initial List: " );
PrintList(head);
DeleteLesserNodes( ref head, K);
Console.Write( "\nFinal List: " );
PrintList(head);
}
} |
Javascript
// JavaScript Program to delete all the nodes from the list // that are lesser than then specified value k // structure of a node class Node{ constructor(data){
this .data = data;
this .next = null ;
}
} // function to get a new node function getNode(data){
let newNode = new Node(data);
return newNode;
} // function to delete all the nodes from the list // that are lesser than the specified value k function deleteLesserNodes(head_ref, K){
let temp = head_ref;
let prev;
// If head node itself holds the value lesser than 'K'
while (temp != null && temp.data < K){
head_ref = temp.next; // changed head
temp = head_ref; // change temp
}
// Delete occurrences other than head
while (temp != null ){
// search for the node to be deleted,
// keep track of the previous node as we
// need to change 'prev->next'
while (temp != null && temp.data >= K){
prev = temp;
temp = temp.next;
}
// If required value nodes was not present
// in linked list
if (temp == null )
return head_ref;
// unlink the node from linked list
prev.next = temp.next;
// Update temp for next iteration of
// outer loop
temp = prev.next;
}
return head_ref;
} // function to a print a linked list function printList(head){
while (head != null ){
console.log(head.data + " " );
head = head.next;
}
} // Driver code let head = getNode(12); head.next = getNode(15); head.next.next = getNode(9); head.next.next.next = getNode(11); head.next.next.next.next = getNode(5); head.next.next.next.next.next = getNode(6); let K = 9; console.log( "Initial List:" );
printList(head); head = deleteLesserNodes(head, K); console.log( "Final List:" );
printList(head); // This code is contributed by Kirti Agarwal |
Output:
Initial List: 12 15 9 11 5 6 Final List: 12 15 9 11
Time Complexity: O(N)
Auxiliary Space: O(1)