Dada una lista doblemente enlazada que contiene N Nodes, la tarea es eliminar todos los Nodes pares de la lista.
Ejemplos:
Entrada: Lista inicial = 15 <=> 16 <=> 6 <=> 7 <=> 17
Salida: Lista final = 15 <=> 7 <=> 17
Explicación: 16 y 6 son Nodes pares. Así que tenemos que eliminarlos.Entrada: Lista inicial = 5 <=> 3 <=> 6 <=> 8 <=> 4 <=> 1 <=> 2 <=> 9
Salida: Lista final = 5 <=> 3 <=> 1 <= > 9
La idea es atravesar los Nodes de la lista doblemente enlazada uno por uno y obtener el puntero de los Nodes que tienen datos parejos. Elimine esos Nodes siguiendo el enfoque utilizado en esta publicación.
A continuación se muestra la implementación de la idea anterior:
C++
// C++ implementation to delete all
// the even nodes from the doubly
// linked list
#include <bits/stdc++.h>
using namespace std;
// Node of the doubly linked list
struct Node {
int data;
Node *prev, *next;
};
// function to insert a node at the beginning
// of the Doubly Linked List
void push(Node** head_ref, int new_data)
{
// allocate node
Node* new_node = new Node();
// put in the data
new_node->data = new_data;
// since we are adding at the beginning,
// prev is always NULL
new_node->prev = NULL;
// link the old list off the new node
new_node->next = (*head_ref);
// change prev of head node to new node
if ((*head_ref) != NULL)
(*head_ref)->prev = new_node;
// move the head to point to the new node
(*head_ref) = new_node;
}
// function to delete a node in a Doubly Linked List.
// head_ref --> pointer to head node pointer.
// del --> pointer to node to be deleted
void deleteNode(Node** head_ref, Node* del)
{
// base case
if (*head_ref == NULL || del == NULL)
return;
// If node to be deleted is head node
if (*head_ref == del)
*head_ref = del->next;
// Change next only if node to be
// deleted is NOT the last node
if (del->next != NULL)
del->next->prev = del->prev;
// Change prev only if node to be
// deleted is NOT the first node
if (del->prev != NULL)
del->prev->next = del->next;
// Finally, free the memory occupied by del
free(del);
return;
}
// function to delete all the even nodes
// from the doubly linked list
void deleteEvenNodes(Node** head_ref)
{
Node* ptr = *head_ref;
Node* next;
while (ptr != NULL) {
next = ptr->next;
// if true, delete node 'ptr'
if (ptr->data % 2 == 0)
deleteNode(head_ref, ptr);
ptr = next;
}
}
// function to print nodes in a
// given doubly linked list
void printList(Node* head)
{
while (head != NULL) {
cout << head->data << " ";
head = head->next;
}
}
// Driver program
int main()
{
// start with the empty list
Node* head = NULL;
// create the doubly linked list
// 15 <-> 16 <-> 7 <-> 6 <-> 17
push(&head, 17);
push(&head, 6);
push(&head, 7);
push(&head, 16);
push(&head, 15);
cout << "Original List: ";
printList(head);
deleteEvenNodes(&head);
cout << "\nModified List: ";
printList(head);
}
Java
// Java implementation to delete all
// the even nodes from the doubly
// linked list
class GFG
{
// Node of the doubly linked list
static class Node
{
int data;
Node prev, next;
};
// function to insert a node at the beginning
// of the Doubly Linked List
static Node push(Node head_ref, int new_data)
{
// allocate node
Node new_node = new Node();
// put in the data
new_node.data = new_data;
// since we are adding at the beginning,
// prev is always null
new_node.prev = null;
// link the old list off the new node
new_node.next = (head_ref);
// change prev of head node to new node
if ((head_ref) != null)
(head_ref).prev = new_node;
// move the head to point to the new node
(head_ref) = new_node;
return head_ref;
}
// function to delete a node in a Doubly Linked List.
// head_ref -. pointer to head node pointer.
// del -. pointer to node to be deleted
static Node deleteNode(Node head_ref, Node del)
{
// base case
if (head_ref == null || del == null)
return null;
// If node to be deleted is head node
if (head_ref == del)
head_ref = del.next;
// Change next only if node to be
// deleted is NOT the last node
if (del.next != null)
del.next.prev = del.prev;
// Change prev only if node to be
// deleted is NOT the first node
if (del.prev != null)
del.prev.next = del.next;
return head_ref;
}
// function to delete all the even nodes
// from the doubly linked list
static Node deleteEvenNodes(Node head_ref)
{
Node ptr = head_ref;
Node next;
while (ptr != null)
{
next = ptr.next;
// if true, delete node 'ptr'
if (ptr.data % 2 == 0)
deleteNode(head_ref, ptr);
ptr = next;
}
return head_ref;
}
// function to print nodes in a
// given doubly linked list
static void printList(Node head)
{
while (head != null)
{
System.out.print( head.data + " ");
head = head.next;
}
}
// Driver code
public static void main(String args[])
{
// start with the empty list
Node head = null;
// create the doubly linked list
// 15 <. 16 <. 7 <. 6 <. 17
head = push(head, 17);
head = push(head, 6);
head = push(head, 7);
head = push(head, 16);
head = push(head, 15);
System.out.print("Original List: ");
printList(head);
head=deleteEvenNodes(head);
System.out.print( "\nModified List: ");
printList(head);
}
}
// This code is contributed by Arnab Kundu
Python3
# Python3 implementation to delete all
# the even nodes from the doubly
# linked list
import math
# Node of the doubly linked list
class Node:
def __init__(self, data):
self.data = data
self.next = None
# function to insert a node at the beginning
# of the Doubly Linked List
def push(head_ref, new_data):
# allocate node
new_node = Node(new_data)
# put in the data
new_node.data = new_data
# since we are adding at the beginning,
# prev is always None
new_node.prev = None
# link the old list off the new node
new_node.next = head_ref
# change prev of head node to new node
if (head_ref!= None):
head_ref.prev = new_node
# move the head to point to the new node
head_ref = new_node
return head_ref
# function to delete a node in a Doubly Linked List.
# head_ref --> pointer to head node pointer.
# del --> pointer to node to be deleted
def deleteNode(head_ref, delete):
# base case
if (head_ref == None or delete == None):
return
# If node to be deleted is head node
if (head_ref == delete):
head_ref = delete.next
# Change next only if node to be
# deleted is NOT the last node
if (delete.next != None):
delete.next.prev = delete.prev
# Change prev only if node to be
# deleted is NOT the first node
if (delete.prev != None):
delete.prev.next = delete.next
# Finally, free the memory occupied by del
return head_ref
# function to delete all the even nodes
# from the doubly linked list
def deleteEvenNodes(head_ref):
ptr = head_ref
next = None
while (ptr != None):
next = ptr.next
# if true, delete node 'ptr'
if (ptr.data % 2 == 0):
deleteNode(head_ref, ptr)
ptr = next
# function to print nodes in a
# given doubly linked list
def printList(head):
while (head != None) :
print(head.data, end = " ")
head = head.next
# Driver Code
if __name__=='__main__':
# start with the empty list
head = None
# create the doubly linked list
# 15 <-> 16 <-> 7 <-> 6 <-> 17
head = push(head, 17)
head = push(head, 6)
head = push(head, 7)
head = push(head, 16)
head = push(head, 15)
print("Original List: ", end = "")
printList(head)
deleteEvenNodes(head)
print("\nModified List: ", end = "")
printList(head)
# This code is contributed by Srathore
C#
// C# implementation to delete all
// the even nodes from the doubly
// linked list
using System;
class GFG
{
// Node of the doubly linked list
public class Node
{
public int data;
public Node prev, next;
};
// function to insert a node at the beginning
// of the Doubly Linked List
static Node push(Node head_ref, int new_data)
{
// allocate node
Node new_node = new Node();
// put in the data
new_node.data = new_data;
// since we are adding at the beginning,
// prev is always null
new_node.prev = null;
// link the old list off the new node
new_node.next = (head_ref);
// change prev of head node to new node
if ((head_ref) != null)
(head_ref).prev = new_node;
// move the head to point to the new node
(head_ref) = new_node;
return head_ref;
}
// function to delete a node in a Doubly Linked List.
// head_ref -. pointer to head node pointer.
// del -. pointer to node to be deleted
static Node deleteNode(Node head_ref, Node del)
{
// base case
if (head_ref == null || del == null)
return null;
// If node to be deleted is head node
if (head_ref == del)
head_ref = del.next;
// Change next only if node to be
// deleted is NOT the last node
if (del.next != null)
del.next.prev = del.prev;
// Change prev only if node to be
// deleted is NOT the first node
if (del.prev != null)
del.prev.next = del.next;
return head_ref;
}
// function to delete all the even nodes
// from the doubly linked list
static Node deleteEvenNodes(Node head_ref)
{
Node ptr = head_ref;
Node next;
while (ptr != null)
{
next = ptr.next;
// if true, delete node 'ptr'
if (ptr.data % 2 == 0)
deleteNode(head_ref, ptr);
ptr = next;
}
return head_ref;
}
// function to print nodes in a
// given doubly linked list
static void printList(Node head)
{
while (head != null)
{
Console.Write( head.data + " ");
head = head.next;
}
}
// Driver code
public static void Main(String []args)
{
// start with the empty list
Node head = null;
// create the doubly linked list
// 15 <. 16 <. 7 <. 6 <. 17
head = push(head, 17);
head = push(head, 6);
head = push(head, 7);
head = push(head, 16);
head = push(head, 15);
Console.Write("Original List: ");
printList(head);
head=deleteEvenNodes(head);
Console.Write( "\nModified List: ");
printList(head);
}
}
/* This code is contributed by PrinciRaj1992 */
Javascript
<script>
// javascript implementation to delete all
// the even nodes from the doubly
// linked list
// Node of the doubly linked list
class Node {
constructor(val) {
this.data = val;
this.prev = null;
this.next = null;
}
}
// function to insert a node at the beginning
// of the Doubly Linked List
function push(head_ref , new_data)
{
// allocate node
var new_node = new Node();
// put in the data
new_node.data = new_data;
// since we are adding at the beginning,
// prev is always null
new_node.prev = null;
// link the old list off the new node
new_node.next = (head_ref);
// change prev of head node to new node
if ((head_ref) != null)
(head_ref).prev = new_node;
// move the head to point to the new node
(head_ref) = new_node;
return head_ref;
}
// function to delete a node in a Doubly Linked List.
// head_ref -. pointer to head node pointer.
// del -. pointer to node to be deleted
function deleteNode(head_ref, del)
{
// base case
if (head_ref == null || del == null)
return null;
// If node to be deleted is head node
if (head_ref == del)
head_ref = del.next;
// Change next only if node to be
// deleted is NOT the last node
if (del.next != null)
del.next.prev = del.prev;
// Change prev only if node to be
// deleted is NOT the first node
if (del.prev != null)
del.prev.next = del.next;
return head_ref;
}
// function to delete all the even nodes
// from the doubly linked list
function deleteEvenNodes(head_ref)
{
var ptr = head_ref;
var next;
while (ptr != null)
{
next = ptr.next;
// if true, delete node 'ptr'
if (ptr.data % 2 == 0)
deleteNode(head_ref, ptr);
ptr = next;
}
return head_ref;
}
// function to print nodes in a
// given doubly linked list
function printList(head)
{
while (head != null)
{
document.write( head.data + " ");
head = head.next;
}
}
// Driver code
// start with the empty list
var head = null;
// create the doubly linked list
// 15 <. 16 <. 7 <. 6 <. 17
head = push(head, 17);
head = push(head, 6);
head = push(head, 7);
head = push(head, 16);
head = push(head, 15);
document.write("Original List: ");
printList(head);
head=deleteEvenNodes(head);
document.write( "<br/>Modified List: ");
printList(head);
// This code contributed by Rajput-Ji
</script>
Producción:
Original List: 15 16 7 6 17 Modified List: 15 7 17
Complejidad temporal: O(N), donde N es el número total de Nodes.
Espacio Auxiliar: O(1)