Dada una lista enlazada individualmente, escriba una función para intercambiar elementos por pares. Por ejemplo, si la lista enlazada es 1->2->3->4->5->6->7 entonces la función debería cambiarla a 2->1->4->3->6->5 ->7, y si la lista enlazada es 1->2->3->4->5->6 entonces la función debería cambiarla a 2->1->4->3->6->5
Este problema ha sido discutido aquí . La solución proporcionada allí intercambia datos de Nodes. Si los datos contienen muchos campos, habrá muchas operaciones de intercambio. Así que cambiar enlaces es una mejor idea en general. La siguiente es la implementación que cambia los enlaces en lugar de intercambiar datos.
Implementación:
C++
/* This program swaps the nodes of
linked list rather than swapping the
field from the nodes.
Imagine a case where a node contains
many fields, there will be plenty
of unnecessary swap calls. */
#include <bits/stdc++.h>
using namespace std;
/* A linked list node */
class node {
public:
int data;
node* next;
};
/* Function to pairwise swap elements
of a linked list. It returns head of
the modified list, so return value
of this node must be assigned */
node* pairWiseSwap(node* head)
{
// If linked list is empty or
// there is only one node in list
if (head == NULL || head->next == NULL)
return head;
// Initialize previous and current pointers
node* prev = head;
node* curr = head->next;
head = curr; // Change head before proceeding
// Traverse the list
while (true) {
node* next = curr->next;
curr->next = prev; // Change next of
// current as previous node
// If next NULL or next is the last node
if (next == NULL || next->next == NULL) {
prev->next = next;
break;
}
// Change next of previous to next of next
prev->next = next->next;
// Update previous and curr
prev = next;
curr = prev->next;
}
return head;
}
/* Function to add a node at
the beginning of 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;
/* link the old list off the new node */
new_node->next = (*head_ref);
/* move the head to point to the new node */
(*head_ref) = new_node;
}
/* Function to print nodes
in a given linked list */
void printList(node* node)
{
while (node != NULL) {
cout << node->data << " ";
node = node->next;
}
}
/* Driver code */
int main()
{
node* start = NULL;
/* The constructed linked list is:
1->2->3->4->5->6->7 */
push(&start, 7);
push(&start, 6);
push(&start, 5);
push(&start, 4);
push(&start, 3);
push(&start, 2);
push(&start, 1);
cout << "Linked list before "
<< "calling pairWiseSwap() ";
printList(start);
start = pairWiseSwap(start); // NOTE THIS CHANGE
cout << "\nLinked list after calling"
<< "pairWiseSwap() ";
printList(start);
return 0;
}
// This code is contributed by Manoj N
C
/* This program swaps the nodes of linked list rather than swapping the
field from the nodes.
Imagine a case where a node contains many fields, there will be plenty
of unnecessary swap calls. */
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
/* A linked list node */
struct Node {
int data;
struct Node* next;
};
/* Function to pairwise swap elements of a linked list */
void pairWiseSwap(struct Node** head)
{
// If linked list is empty or there is only one node in list
if (*head == NULL || (*head)->next == NULL)
return;
// Initialize previous and current pointers
struct Node* prev = *head;
struct Node* curr = (*head)->next;
*head = curr; // Change head before proceeding
// Traverse the list
while (true) {
struct Node* next = curr->next;
curr->next = prev; // Change next of current as previous node
// If next NULL or next is the last node
if (next == NULL || next->next == NULL) {
prev->next = next;
break;
}
// Change next of previous to next next
prev->next = next->next;
// Update previous and curr
prev = next;
curr = prev->next;
}
}
/* Function to add a node at the beginning of Linked List */
void push(struct Node** head_ref, int new_data)
{
/* allocate node */
struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
/* put in the data */
new_node->data = new_data;
/* link the old list off the new node */
new_node->next = (*head_ref);
/* move the head to point to the new node */
(*head_ref) = new_node;
}
/* Function to print nodes in a given linked list */
void printList(struct Node* node)
{
while (node != NULL) {
printf("%d ", node->data);
node = node->next;
}
}
/* Driver program to test above function */
int main()
{
struct Node* start = NULL;
/* The constructed linked list is:
1->2->3->4->5->6->7 */
push(&start, 7);
push(&start, 6);
push(&start, 5);
push(&start, 4);
push(&start, 3);
push(&start, 2);
push(&start, 1);
printf("\n Linked list before calling pairWiseSwap() ");
printList(start);
pairWiseSwap(&start);
printf("\n Linked list after calling pairWiseSwap() ");
printList(start);
getchar();
return 0;
}
Java
// Java program to swap elements of linked list by changing links
class LinkedList {
static Node head;
static class Node {
int data;
Node next;
Node(int d)
{
data = d;
next = null;
}
}
/* Function to pairwise swap elements of a linked list */
Node pairWiseSwap(Node node)
{
// If linked list is empty or there is only one node in list
if (node == null || node.next == null) {
return node;
}
// Initialize previous and current pointers
Node prev = node;
Node curr = node.next;
node = curr; // Change head before proceeding
// Traverse the list
while (true) {
Node next = curr.next;
curr.next = prev; // Change next of current as previous node
// If next NULL or next is the last node
if (next == null || next.next == null) {
prev.next = next;
break;
}
// Change next of previous to next next
prev.next = next.next;
// Update previous and curr
prev = next;
curr = prev.next;
}
return node;
}
/* Function to print nodes in a given linked list */
void printList(Node node)
{
while (node != null) {
System.out.print(node.data + " ");
node = node.next;
}
}
// Driver program to test above functions
public static void main(String[] args)
{
/* The constructed linked list is:
1->2->3->4->5->6->7 */
LinkedList list = new LinkedList();
list.head = new Node(1);
list.head.next = new Node(2);
list.head.next.next = new Node(3);
list.head.next.next.next = new Node(4);
list.head.next.next.next.next = new Node(5);
list.head.next.next.next.next.next = new Node(6);
list.head.next.next.next.next.next.next = new Node(7);
System.out.println("Linked list before calling pairwiseSwap() ");
list.printList(head);
Node st = list.pairWiseSwap(head);
System.out.println("");
System.out.println("Linked list after calling pairwiseSwap() ");
list.printList(st);
System.out.println("");
}
}
// This code has been contributed by Mayank Jaiswal
Python3
# Python3 program to swap elements of
# linked list by changing links
# Linked List Node
class Node:
def __init__(self, data):
self.data = data
self.next = None
# Create and Handle list operations
class LinkedList:
def __init__(self):
# Head of list
self.head = None
# Add data to list
def addToList(self, data):
newNode = Node(data)
if self.head is None:
self.head = newNode
return
last = self.head
while last.next:
last = last.next
last.next = newNode
# Function to print nodes
# in a given linked list
def __str__(self):
linkedListStr = ""
temp = self.head
while temp:
linkedListStr = (linkedListStr +
str(temp.data) + " ")
temp = temp.next
return linkedListStr
# Function to pairwise swap elements
# of a linked list. It returns head of
# the modified list, so return value
# of this node must be assigned
def pairWiseSwap(self):
# If list is empty or with one node
if (self.head is None or
self.head.next is None):
return
# Initialize previous and current pointers
prevNode = self.head
currNode = self.head.next
# Change head node
self.head = currNode
# Traverse the list
while True:
nextNode = currNode.next
# Change next of current
# node to previous node
currNode.next = prevNode
# If next node is the last node
if nextNode.next is None:
prevNode.next = nextNode
break
# Change next of previous to
# next of next
prevNode.next = nextNode.next
# Update previous and current nodes
prevNode = nextNode
currNode = prevNode.next
# Driver Code
linkedList = LinkedList()
linkedList.addToList(1)
linkedList.addToList(2)
linkedList.addToList(3)
linkedList.addToList(4)
linkedList.addToList(5)
linkedList.addToList(6)
linkedList.addToList(7)
print("Linked list before calling"
"pairwiseSwap() ",
linkedList)
linkedList.pairWiseSwap()
print("Linked list after calling "
"pairwiseSwap() ",
linkedList)
# This code is contributed by AmiyaRanjanRout
C#
// C# program to swap elements of
// linked list by changing links
using System;
public class LinkedList {
Node head;
public class Node {
public int data;
public Node next;
public Node(int d)
{
data = d;
next = null;
}
}
/* Function to pairwise swap
elements of a linked list */
Node pairWiseSwap(Node node)
{
// If linked list is empty or there
// is only one node in list
if (node == null || node.next == null) {
return node;
}
// Initialize previous and current pointers
Node prev = node;
Node curr = node.next;
// Change head before proceeding
node = curr;
// Traverse the list
while (true) {
Node next = curr.next;
// Change next of current as previous node
curr.next = prev;
// If next NULL or next is the last node
if (next == null || next.next == null) {
prev.next = next;
break;
}
// Change next of previous to next of next
prev.next = next.next;
// Update previous and curr
prev = next;
curr = prev.next;
}
return node;
}
/* Function to print nodes
in a given linked list */
void printList(Node node)
{
while (node != null) {
Console.Write(node.data + " ");
node = node.next;
}
}
// Driver code
public static void Main(String[] args)
{
/* The constructed linked list is:
1->2->3->4->5->6->7 */
LinkedList list = new LinkedList();
list.head = new Node(1);
list.head.next = new Node(2);
list.head.next.next = new Node(3);
list.head.next.next.next = new Node(4);
list.head.next.next.next.next = new Node(5);
list.head.next.next.next.next.next = new Node(6);
list.head.next.next.next.next.next.next = new Node(7);
Console.WriteLine("Linked list before calling pairwiseSwap() ");
list.printList(list.head);
Node st = list.pairWiseSwap(list.head);
Console.WriteLine("");
Console.WriteLine("Linked list after calling pairwiseSwap() ");
list.printList(st);
Console.WriteLine("");
}
}
// This code contributed by Rajput-Ji
Javascript
<script>
// javascript program to swap elements of linked list by changing links
var head;
class Node {
constructor(val) {
this.data = val;
this.next = null;
}
}
/* Function to pairwise swap elements of a linked list */
function pairWiseSwap(node) {
// If linked list is empty or there is only one node in list
if (node == null || node.next == null) {
return node;
}
// Initialize previous and current pointers
var prev = node;
var curr = node.next;
node = curr; // Change head before proceeding
// Traverse the list
while (true) {
var next = curr.next;
curr.next = prev; // Change next of current as previous node
// If next NULL or next is the last node
if (next == null || next.next == null) {
prev.next = next;
break;
}
// Change next of previous to next next
prev.next = next.next;
// Update previous and curr
prev = next;
curr = prev.next;
}
return node;
}
/* Function to print nodes in a given linked list */
function printList(node) {
while (node != null) {
document.write(node.data + " ");
node = node.next;
}
}
// Driver program to test above functions
/*
* The constructed linked list is: 1->2->3->4->5->6->7
*/
head = new Node(1);
head.next = new Node(2);
head.next.next = new Node(3);
head.next.next.next = new Node(4);
head.next.next.next.next = new Node(5);
head.next.next.next.next.next = new Node(6);
head.next.next.next.next.next.next = new Node(7);
document.write("Linked list before calling pairwiseSwap() ");
printList(head);
var st = pairWiseSwap(head);
document.write("<br/>");
document.write("Linked list after calling pairwiseSwap() ");
printList(st);
document.write("");
// This code contributed by aashish1995
</script>
Producción
Linked list before calling pairWiseSwap() 1 2 3 4 5 6 7 Linked list after callingpairWiseSwap() 2 1 4 3 6 5 7
Complejidad de tiempo: La complejidad de tiempo del programa anterior es O(n) donde n es el número de Nodes en una lista enlazada dada. El bucle while realiza un recorrido de la lista enlazada dada.
Espacio auxiliar : O (1) ya que usa espacio constante para rastrear anterior y siguiente
A continuación se muestra la implementación recursiva del mismo enfoque. Cambiamos los dos primeros Nodes y recurrimos para la lista restante. Gracias a geek y omer salem por sugerir este método.
Implementación:
C++
/* This program swaps the nodes of linked list rather than swapping the
field from the nodes.
Imagine a case where a node contains many fields, there will be plenty
of unnecessary swap calls. */
#include <bits/stdc++.h>
using namespace std;
/* A linked list node */
class node {
public:
int data;
node* next;
};
/* Function to pairwise swap elements of a linked list.
It returns head of the modified list, so return value
of this node must be assigned */
node* pairWiseSwap(node* head)
{
// Base Case: The list is empty or has only one node
if (head == NULL || head->next == NULL)
return head;
// Store head of list after two nodes
node* remaining = head->next->next;
// Change head
node* newhead = head->next;
// Change next of second node
head->next->next = head;
// Recur for remaining list and change next of head
head->next = pairWiseSwap(remaining);
// Return new head of modified list
return newhead;
}
/* Function to add a node at the beginning of 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;
/* link the old list off the new node */
new_node->next = (*head_ref);
/* move the head to point to the new node */
(*head_ref) = new_node;
}
/* Function to print nodes in a given linked list */
void printList(node* node)
{
while (node != NULL) {
cout << node->data << " ";
node = node->next;
}
}
/* Driver program to test above function */
int main()
{
node* start = NULL;
/* The constructed linked list is:
1->2->3->4->5->6->7 */
push(&start, 7);
push(&start, 6);
push(&start, 5);
push(&start, 4);
push(&start, 3);
push(&start, 2);
push(&start, 1);
cout << "Linked list before calling pairWiseSwap() ";
printList(start);
start = pairWiseSwap(start); // NOTE THIS CHANGE
cout << "\nLinked list after calling pairWiseSwap() ";
printList(start);
return 0;
}
// This is code is contributed by rathbhupendra
C
/* This program swaps the nodes of linked list rather than swapping the
field from the nodes.
Imagine a case where a node contains many fields, there will be plenty
of unnecessary swap calls. */
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
/* A linked list node */
struct node {
int data;
struct node* next;
};
/* Function to pairwise swap elements of a linked list.
It returns head of the modified list, so return value
of this node must be assigned */
struct node* pairWiseSwap(struct node* head)
{
// Base Case: The list is empty or has only one node
if (head == NULL || head->next == NULL)
return head;
// Store head of list after two nodes
struct node* remaining = head->next->next;
// Change head
struct node* newhead = head->next;
// Change next of second node
head->next->next = head;
// Recur for remaining list and change next of head
head->next = pairWiseSwap(remaining);
// Return new head of modified list
return newhead;
}
/* Function to add a node at the beginning of Linked List */
void push(struct node** head_ref, int new_data)
{
/* allocate node */
struct node* new_node = (struct node*)malloc(sizeof(struct node));
/* put in the data */
new_node->data = new_data;
/* link the old list off the new node */
new_node->next = (*head_ref);
/* move the head to point to the new node */
(*head_ref) = new_node;
}
/* Function to print nodes in a given linked list */
void printList(struct node* node)
{
while (node != NULL) {
printf("%d ", node->data);
node = node->next;
}
}
/* Driver program to test above function */
int main()
{
struct node* start = NULL;
/* The constructed linked list is:
1->2->3->4->5->6->7 */
push(&start, 7);
push(&start, 6);
push(&start, 5);
push(&start, 4);
push(&start, 3);
push(&start, 2);
push(&start, 1);
printf("\n Linked list before calling pairWiseSwap() ");
printList(start);
start = pairWiseSwap(start); // NOTE THIS CHANGE
printf("\n Linked list after calling pairWiseSwap() ");
printList(start);
return 0;
}
Java
// Java program to swap elements of linked list by changing links
class LinkedList {
static Node head;
static class Node {
int data;
Node next;
Node(int d)
{
data = d;
next = null;
}
}
/* Function to pairwise swap elements of a linked list.
It returns head of the modified list, so return value
of this node must be assigned */
Node pairWiseSwap(Node node)
{
// Base Case: The list is empty or has only one node
if (node == null || node.next == null) {
return node;
}
// Store head of list after two nodes
Node remaining = node.next.next;
// Change head
Node newhead = node.next;
// Change next of second node
node.next.next = node;
// Recur for remaining list and change next of head
node.next = pairWiseSwap(remaining);
// Return new head of modified list
return newhead;
}
/* Function to print nodes in a given linked list */
void printList(Node node)
{
while (node != null) {
System.out.print(node.data + " ");
node = node.next;
}
}
// Driver program to test above functions
public static void main(String[] args)
{
/* The constructed linked list is:
1->2->3->4->5->6->7 */
LinkedList list = new LinkedList();
list.head = new Node(1);
list.head.next = new Node(2);
list.head.next.next = new Node(3);
list.head.next.next.next = new Node(4);
list.head.next.next.next.next = new Node(5);
list.head.next.next.next.next.next = new Node(6);
list.head.next.next.next.next.next.next = new Node(7);
System.out.println("Linked list before calling pairwiseSwap() ");
list.printList(head);
head = list.pairWiseSwap(head);
System.out.println("");
System.out.println("Linked list after calling pairwiseSwap() ");
list.printList(head);
System.out.println("");
}
}
Python3
# Python3 program to pairwise swap
# linked list using recursive method
# Linked List Node
class Node:
def __init__(self, data):
self.data = data
self.next = None
# Create and Handle list operations
class LinkedList:
def __init__(self):
# Head of list
self.head = None
# Add data to list
def addToList(self, data):
newNode = Node(data)
if self.head is None:
self.head = newNode
return
last = self.head
while last.next:
last = last.next
last.next = newNode
# Function to print nodes in
# a given linked list
def __str__(self):
linkedListStr = ""
temp = self.head
while temp:
linkedListStr = (linkedListStr +
str(temp.data) + " ")
temp = temp.next
return linkedListStr
# Function to pairwise swap elements of
# a linked list.It returns head of the
# modified list, so return value
# of this node must be assigned
def pairWiseSwap(self, node):
# If list is empty or with one node
if node is None or node.next is None:
return node
# Store head of list after 2 nodes
remaining = node.next.next
# Change head
newHead = node.next
# Change next to second node
node.next.next = node
# Recur for remaining list and
# change next of head
node.next = self.pairWiseSwap(remaining)
# Return new head of modified list
return newHead
# Driver Code
linkedList = LinkedList()
linkedList.addToList(1)
linkedList.addToList(2)
linkedList.addToList(3)
linkedList.addToList(4)
linkedList.addToList(5)
linkedList.addToList(6)
linkedList.addToList(7)
print("Linked list before calling "
"pairwiseSwap() ", linkedList)
linkedList.head = linkedList.pairWiseSwap(
linkedList.head)
print("Linked list after calling "
"pairwiseSwap() ", linkedList)
# This code is contributed by AmiyaRanjanRout
C#
// C# program to swap elements
// of linked list by changing links
using System;
public class LinkedList {
Node head;
class Node {
public int data;
public Node next;
public Node(int d)
{
data = d;
next = null;
}
}
/* Function to pairwise swap
elements of a linked list.
It returns head of the modified
list, so return value of this
node must be assigned */
Node pairWiseSwap(Node node)
{
// Base Case: The list is empty
// or has only one node
if (node == null || node.next == null) {
return node;
}
// Store head of list after two nodes
Node remaining = node.next.next;
// Change head
Node newhead = node.next;
// Change next of second node
node.next.next = node;
// Recur for remaining list
// and change next of head
node.next = pairWiseSwap(remaining);
// Return new head of modified list
return newhead;
}
/* Function to print nodes in a given linked list */
void printList(Node node)
{
while (node != null) {
Console.Write(node.data + " ");
node = node.next;
}
}
// Driver program to test above functions
public static void Main()
{
/* The constructed linked list is:
1->2->3->4->5->6->7 */
LinkedList list = new LinkedList();
list.head = new Node(1);
list.head.next = new Node(2);
list.head.next.next = new Node(3);
list.head.next.next.next = new Node(4);
list.head.next.next.next.next = new Node(5);
list.head.next.next.next.next.next = new Node(6);
list.head.next.next.next.next.next.next = new Node(7);
Console.WriteLine("Linked list before calling pairwiseSwap() ");
list.printList(list.head);
list.head = list.pairWiseSwap(list.head);
Console.WriteLine("");
Console.WriteLine("Linked list after calling pairwiseSwap() ");
list.printList(list.head);
Console.WriteLine("");
}
}
// This code is contributed by PrinciRaj1992
Javascript
<script>
// javascript program to swap elements of linked list by changing links
var head;
class Node {
constructor(val) {
this.data = val;
this.next = null;
}
}
/*
* Function to pairwise swap elements of a linked It returns head of the
* modified list, so return value of this node must be assigned
*/
function pairWiseSwap(node) {
// Base Case: The list is empty or has only one node
if (node == null || node.next == null) {
return node;
}
// Store head of list after two nodes
var remaining = node.next.next;
// Change head
var newhead = node.next;
// Change next of second node
node.next.next = node;
// Recur for remaining list and change next of head
node.next = pairWiseSwap(remaining);
// Return new head of modified list
return newhead;
}
/* Function to print nodes in a given linked list */
function printList(node) {
while (node != null) {
document.write(node.data + " ");
node = node.next;
}
}
// Driver program to test above functions
/*
* The constructed linked list is: 1->2->3->4->5->6->7
*/
head = new Node(1);
head.next = new Node(2);
head.next.next = new Node(3);
head.next.next.next = new Node(4);
head.next.next.next.next = new Node(5);
head.next.next.next.next.next = new Node(6);
head.next.next.next.next.next.next = new Node(7);
document.write("Linked list before calling pairwiseSwap() ");
printList(head);
head = pairWiseSwap(head);
document.write("<br/>");
document.write("Linked list after calling pairwiseSwap() ");
printList(head);
document.write("");
// This code contributed by umadevi9616
</script>
Producción
Linked list before calling pairWiseSwap() 1 2 3 4 5 6 7 Linked list after calling pairWiseSwap() 2 1 4 3 6 5 7
Complejidad temporal: O(n)
Espacio auxiliar: O(n)
Publicación traducida automáticamente
Artículo escrito por GeeksforGeeks-1 y traducido por Barcelona Geeks. The original can be accessed here. Licence: CCBY-SA