Delete linked list nodes which have a Lesser Value on Left Side
Given a singly linked list, the task is to remove all the nodes which have a lesser value on left side.
Examples:
Input: 12->15->10->11->5->6->2->3 Output: Modified Linked List = 12 -> 10 -> 5 -> 2 Input: 25->15->6->48->12->5->16->14 Output: Modified Linked List = 25 -> 15 -> 6 -> 5
Approach:
- Initialize a varaible maximum with head node.
- Traverse the list.
- Check if the next node is lesser than max_node. If yes, the move to the next node.
- Else If not, then update the value of max_node and delete the next node.
Below is the implementation of above approach:
C++
// C++ implementation of above approach#include <bits/stdc++.h>using namespace std; // Structure of a linked list nodestruct Node { int data; struct Node* next;}; // Function to Delete nodes which have// greater value node(s) on right sidevoid delNodes(struct Node* head){ struct Node* current = head; // Initialize max struct Node* maxnode = head; struct Node* temp; while (current != NULL && current->next != NULL) { // If current is greater than max, // then update max and move current if (current->next->data <= maxnode->data) { current = current->next; maxnode = current; } // If current is smaller than max, then delete current else { temp = current->next; current->next = temp->next; free(temp); } }} /* Utility function to insert a node at the beginning */void push(struct Node** head_ref, int new_data){ struct Node* new_node = new Node; new_node->data = new_data; new_node->next = *head_ref; *head_ref = new_node;} /* Utility function to print a linked list */void printList(struct Node* head){ while (head != NULL) { cout << head->data << " "; head = head->next; } cout << endl;} /* Driver program to test above functions */int main(){ struct Node* head = NULL; /* Create following linked list 12->15->10->11->5->6->2->3 */ push(&head, 3); push(&head, 2); push(&head, 6); push(&head, 5); push(&head, 11); push(&head, 10); push(&head, 15); push(&head, 12); printf("Given Linked List: "); printList(head); delNodes(head); printf("\nModified Linked List: "); printList(head); return 0;} |
Java
// Java implementation of above approach class Solution{ // Structure of a linked list node static class Node { int data; Node next; }; // Function to Delete nodes which have // greater value node(s) on right side static Node delNodes(Node head) { Node current = head; // Initialize max Node maxnode = head; Node temp; while (current != null && current.next != null) { // If current is lesser than max, // then update max and move current if (current.next.data <= maxnode.data) { current = current.next; maxnode = current; } // If current is greater than max, then delete current else { temp = current.next; current.next = temp.next; } } return head;} // Utility function to insert a node at the beginning /static Node push(Node head_ref, int new_data) { Node new_node = new Node(); new_node.data = new_data; new_node.next = head_ref; head_ref = new_node; return head_ref;} // Utility function to print a linked list /static Node printList(Node head) { while (head != null) { System.out.print( head.data + " "); head = head.next; } System.out.println(); return head;} // Driver program to test above functions /public static void main(String args[]) { Node head = null; /* Create following linked list 12->15->10->11->5->6->2->3 */ head=push(head, 3); head=push(head, 2); head=push(head, 6); head=push(head, 5); head=push(head, 11); head=push(head, 10); head=push(head, 15); head=push(head, 12); System.out.printf("Given Linked List \n"); printList(head); head=delNodes(head); System.out.printf("Modified Linked List \n"); printList(head); }} // This code is contributed by Arnab Kundu |
Python3
# Python implementation of above approachimport math # Structure of a linked list nodeclass Node: def __init__(self, data): self.data = data self.next = None # Function to Delete nodes which have# greater value node(s) on right sidedef delNodes(head): current = head # Initialize max maxnode = head temp = None while (current != None and current.next != None): # If current is greater than max, # then update max and move current if (current.next.data <= maxnode.data): current = current.next maxnode = current # If current is smaller than max, # then delete current else: temp = current.next current.next = temp.next #free(temp) # Utility function to insert a node at the beginning def push(head_ref, new_data): new_node = Node(new_data) new_node.data = new_data new_node.next = head_ref head_ref = new_node return head_ref # Utility function to print a linked list def printList(head): while (head != None) : print(head.data, end = " ") head = head.next print() # Driver Codeif __name__=='__main__': head = None # Create following linked list # 12.15.10.11.5.6.2.3 head = push(head, 3) head = push(head, 2) head = push(head, 6) head = push(head, 5) head = push(head, 11) head = push(head, 10) head = push(head, 15) head = push(head, 12) print("Given Linked List: ", end = "") printList(head) delNodes(head) print("\nModified Linked List: ", end = "") printList(head) # This code is contributed by AbhiThakur |
C#
// C# implementation of the above approach: using System;class GFG{ // Structure of a linked list node public class Node { public int data; public Node next; }; // Function to Delete nodes which have // greater value node(s) on right side static Node delNodes(Node head) { Node current = head; // Initialize max Node maxnode = head; Node temp; while (current != null && current.next != null) { // If current is lesser than max, // then update max and move current if (current.next.data <= maxnode.data) { current = current.next; maxnode = current; } // If current is greater than max, // then delete current else { temp = current.next; current.next = temp.next; } } return head;} // Utility function to insert // a node at the beginning static Node push(Node head_ref, int new_data) { Node new_node = new Node(); new_node.data = new_data; new_node.next = head_ref; head_ref = new_node; return head_ref;} // Utility function to print a linked list static Node printList(Node head) { while (head != null) { Console.Write(head.data + " "); head = head.next; } Console.WriteLine(); return head;} // Driver Codepublic static void Main(String []args) { Node head = null; /* Create following linked list 12->15->10->11->5->6->2->3 */ head = push(head, 3); head = push(head, 2); head = push(head, 6); head = push(head, 5); head = push(head, 11); head = push(head, 10); head = push(head, 15); head = push(head, 12); Console.Write("Given Linked List \n"); printList(head); head = delNodes(head); Console.Write("Modified Linked List \n"); printList(head); }} // This code is contributed by PrinciRaj1992 |
Output:
Given Linked List: 12 15 10 11 5 6 2 3 Modified Linked List: 12 10 5 2
Time Complexity: O(N), where N is the total number of nodes.
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