Nodes de intercambio por parejas de una lista vinculada dada

Posted on by Rudeus Greyrat

Dada una lista enlazada individualmente, escriba una función para intercambiar elementos por pares. 

Entrada: 1->2->3->4->5->6->NULO 
Salida: 2->1->4->3->6->5->NULO

Entrada: 1->2->3->4->5->NULO 
Salida: 2->1->4->3->5->NULO

Entrada: 1->NULO 
Salida: 1->NULO 

Por ejemplo, si la lista enlazada es 1->2->3->4->5 entonces la función debería cambiarla a 2->1->4->3->5, y si la lista enlazada es entonces el la función debería cambiarlo a.  

MÉTODO 1 (Iterativo) 

Comience desde el Node principal y recorra la lista. Al atravesar los datos de intercambio de cada Node con los datos de su siguiente Node. 

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A continuación se muestra la implementación del enfoque anterior: 

C++

// C++ program to pairwise swap elements
// in a given linked list
#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 */
void pairWiseSwap(Node* head)
{
    Node* temp = head;
  
    /* Traverse further only if 
    there are at-least two nodes left */
    while (temp != NULL && temp->next != NULL) {
        /* Swap data of node with 
           its next node's data */
        swap(temp->data,
             temp->next->data);
  
        /* Move temp by 2 for the next pair */
        temp = temp->next->next;
    }
}
  
/* 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 */
    push(&start, 5);
    push(&start, 4);
    push(&start, 3);
    push(&start, 2);
    push(&start, 1);
  
    cout << "Linked list "
         << "before calling pairWiseSwap()\n";
    printList(start);
  
    pairWiseSwap(start);
  
    cout << "\nLinked list "
         << "after calling pairWiseSwap()\n";
    printList(start);
  
    return 0;
}
  
// This code is contributed
// by rathbhupendra

C

/* C program to pairwise swap elements in a given linked list */
#include <stdio.h>
#include <stdlib.h>
  
/* A linked list node */
struct Node {
    int data;
    struct Node* next;
};
  
/*Function to swap two integers at addresses a and b */
void swap(int* a, int* b);
  
/* Function to pairwise swap elements of a linked list */
void pairWiseSwap(struct Node* head)
{
    struct Node* temp = head;
  
    /* Traverse further only if there are at-least two nodes left */
    while (temp != NULL && temp->next != NULL) {
        /* Swap data of node with its next node's data */
        swap(&temp->data, &temp->next->data);
  
        /* Move temp by 2 for the next pair */
        temp = temp->next->next;
    }
}
  
/* UTILITY FUNCTIONS */
/* Function to swap two integers */
void swap(int* a, int* b)
{
    int temp;
    temp = *a;
    *a = *b;
    *b = temp;
}
  
/* 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 */
    push(&start, 5);
    push(&start, 4);
    push(&start, 3);
    push(&start, 2);
    push(&start, 1);
  
    printf("Linked list before calling pairWiseSwap()\n");
    printList(start);
  
    pairWiseSwap(start);
  
    printf("\nLinked list after calling pairWiseSwap()\n");
    printList(start);
  
    return 0;
}

Java

// Java program to pairwise swap elements of a linked list
class LinkedList {
    Node head; // head of list
  
    /* Linked list Node*/
    class Node {
        int data;
        Node next;
        Node(int d)
        {
            data = d;
            next = null;
        }
    }
  
    void pairWiseSwap()
    {
        Node temp = head;
  
        /* Traverse only till there are atleast 2 nodes left */
        while (temp != null && temp.next != null) {
  
            /* Swap the data */
            int k = temp.data;
            temp.data = temp.next.data;
            temp.next.data = k;
            temp = temp.next.next;
        }
    }
  
    /* Utility functions */
  
    /* Inserts a new Node at front of the list. */
    public void push(int new_data)
    {
        /* 1 & 2: Allocate the Node &
                  Put in the data*/
        Node new_node = new Node(new_data);
  
        /* 3. Make next of new Node as head */
        new_node.next = head;
  
        /* 4. Move the head to point to new Node */
        head = new_node;
    }
  
    /* Function to print linked list */
    void printList()
    {
        Node temp = head;
        while (temp != null) {
            System.out.print(temp.data + " ");
            temp = temp.next;
        }
        System.out.println();
    }
  
    /* Driver program to test above functions */
    public static void main(String args[])
    {
        LinkedList llist = new LinkedList();
  
        /* Created Linked List 1->2->3->4->5 */
        llist.push(5);
        llist.push(4);
        llist.push(3);
        llist.push(2);
        llist.push(1);
  
        System.out.println("Linked List before calling pairWiseSwap() ");
        llist.printList();
  
        llist.pairWiseSwap();
  
        System.out.println("Linked List after calling pairWiseSwap() ");
        llist.printList();
    }
}
/* This code is contributed by Rajat Mishra */

Python

# Python program to swap the elements of linked list pairwise
  
# Node class
  
  
class Node:
  
    # Constructor to initialize the node object
    def __init__(self, data):
        self.data = data
        self.next = None
  
  
class LinkedList:
  
    # Function to initialize head
    def __init__(self):
        self.head = None
  
    # Function to pairwise swap elements of a linked list
    def pairwiseSwap(self):
        temp = self.head
  
        # There are no nodes in linked list
        if temp is None:
            return
  
        # Traverse furthethr only if there are at least two
        # left
        while(temp and temp.next):
  
            # If both nodes are same,
            # no need to swap data
            if(temp.data != temp.next.data):
  
                # Swap data of node with its next node's data
                temp.data, temp.next.data = temp.next.data, temp.data
  
            # Move temp by 2 to the next pair
            temp = temp.next.next
  
    # Function to insert a new node at the beginning
    def push(self, new_data):
        new_node = Node(new_data)
        new_node.next = self.head
        self.head = new_node
  
    # Utility function to print the linked LinkedList
    def printList(self):
        temp = self.head
        while(temp):
            print temp.data,
            temp = temp.next
  
  
# Driver program
llist = LinkedList()
llist.push(5)
llist.push(4)
llist.push(3)
llist.push(2)
llist.push(1)
  
print "Linked list before calling pairWiseSwap() "
llist.printList()
  
llist.pairwiseSwap()
  
print "\nLinked list after calling pairWiseSwap()"
llist.printList()
  
# This code is contributed by Nikhil Kumar Singh(nickzuck_007)

C#

// C# program to pairwise swap elements of a linked list
using System;
class LinkedList {
    Node head; // head of list
  
    /* Linked list Node*/
    public class Node {
        public int data;
        public Node next;
        public Node(int d)
        {
            data = d;
            next = null;
        }
    }
  
    void pairWiseSwap()
    {
        Node temp = head;
  
        /* Traverse only till there are atleast 2 nodes left */
        while (temp != null && temp.next != null) {
  
            /* Swap the data */
            int k = temp.data;
            temp.data = temp.next.data;
            temp.next.data = k;
            temp = temp.next.next;
        }
    }
  
    /* Utility functions */
  
    /* Inserts a new Node at front of the list. */
    public void push(int new_data)
    {
        /* 1 & 2: Allocate the Node & 
                Put in the data*/
        Node new_node = new Node(new_data);
  
        /* 3. Make next of new Node as head */
        new_node.next = head;
  
        /* 4. Move the head to point to new Node */
        head = new_node;
    }
  
    /* Function to print linked list */
    void printList()
    {
        Node temp = head;
        while (temp != null) {
            Console.Write(temp.data + " ");
            temp = temp.next;
        }
        Console.WriteLine();
    }
  
    /* Driver program to test above functions */
    public static void Main(String[] args)
    {
        LinkedList llist = new LinkedList();
  
        /* Created Linked List 1->2->3->4->5 */
        llist.push(5);
        llist.push(4);
        llist.push(3);
        llist.push(2);
        llist.push(1);
  
        Console.WriteLine("Linked List before calling pairWiseSwap() ");
        llist.printList();
  
        llist.pairWiseSwap();
  
        Console.WriteLine("Linked List after calling pairWiseSwap() ");
        llist.printList();
    }
}
// This code is contributed by Arnab Kundu

JavaScript

<script>
  
// JavaScript program to pairwise swap 
// elements of a linked list
var head; // head of list
  
    /* Linked list Node */
    class Node {
        constructor(val) {
            this.data = val;
            this.next = null;
        }
    }
    function pairWiseSwap() {
var temp = head;
  
        /* Traverse only till there are 
        atleast 2 nodes left */
        while (temp != null && temp.next != null) {
  
            /* Swap the data */
            var k = temp.data;
            temp.data = temp.next.data;
            temp.next.data = k;
            temp = temp.next.next;
        }
    }
  
    /* Utility functions */
  
    /* Inserts a new Node at front of the list. */
     function push(new_data) {
        /*
         * 1 & 2: Allocate the Node & Put in the data
         */
var new_node = new Node(new_data);
  
        /* 3. Make next of new Node as head */
        new_node.next = head;
  
        /* 4. Move the head to point to new Node */
        head = new_node;
    }
  
    /* Function to print linked list */
    function printList() {
var temp = head;
        while (temp != null) {
            document.write(temp.data + " ");
            temp = temp.next;
        }
        document.write("<br/>");
    }
  
    /* Driver program to test above functions */
      
  
  
        /* Created Linked List 1->2->3->4->5 */
        push(5);
        push(4);
        push(3);
        push(2);
        push(1);
  
        document.write(
        "Linked List before calling pairWiseSwap() <br/>"
        );
        printList();
  
        pairWiseSwap();
  
        document.write(
        "Linked List after calling pairWiseSwap()<br/> "
        );
        printList();
  
// This code is contributed by todaysgaurav
  
</script>
Producción

Linked list before calling pairWiseSwap()
1 2 3 4 5 
Linked list after calling pairWiseSwap()
2 1 4 3 5

Complejidad del tiempo: O(N)

A medida que recorremos la lista enlazada solo una vez.

Espacio Auxiliar: O(1)

Como espacio adicional constante se utiliza.

MÉTODO 2 (Recursivo) 
Si hay 2 o más de 2 Nodes en la lista enlazada, intercambie los dos primeros Nodes y llame recursivamente al resto de la lista.

La imagen de abajo es una ejecución en seco del enfoque anterior: 

A continuación se muestra la implementación del enfoque anterior:

C++

/* Recursive function to pairwise swap elements
   of a linked list */
void pairWiseSwap(node* head)
{
    /* There must be at-least two nodes in the list */
    if (head != NULL && head->next != NULL) {
  
        /* Swap the node's data with data of next node */
        swap(head->data, head->next->data);
  
        /* Call pairWiseSwap() for rest of the list */
        pairWiseSwap(head->next->next);
    }
}
  
// The code is contributed by Gautam goel (gautamgoel962)

C

/* Recursive function to pairwise swap elements
   of a linked list */
void pairWiseSwap(struct node* head)
{
    /* There must be at-least two nodes in the list */
    if (head != NULL && head->next != NULL) {
  
        /* Swap the node's data with data of next node */
        swap(head->data, head->next->data);
  
        /* Call pairWiseSwap() for rest of the list */
        pairWiseSwap(head->next->next);
    }
}

Java

/* Recursive function to pairwise swap elements
   of a linked list */
static void pairWiseSwap(node head)
{
    /* There must be at-least two nodes in the list */
    if (head != null && head.next != null) {
  
        /* Swap the node's data with data of next node */
        swap(head.data, head.next.data);
  
        /* Call pairWiseSwap() for rest of the list */
        pairWiseSwap(head.next.next);
    }
}
  
// This code contributed by aashish1995 

Python3

# Recursive function to pairwise swap elements of a linked list 
def pairWiseSwap(head):
  
    # There must be at-least two nodes in the list 
    if (head != None and head.next != None):
   
        # Swap the node's data with data of next node 
        swap(head.data, head.next.data);
   
        # Call pairWiseSwap() for rest of the list 
        pairWiseSwap(head.next.next);
  
# This code is contributed by _saurabh_jaiswal

C#

/* Recursive function to pairwise swap elements
   of a linked list */
static void pairWiseSwap(node head)
{
    /* There must be at-least two nodes in the list */
    if (head != null && head.next != null) {
  
        /* Swap the node's data with data of next node */
        swap(head.data, head.next.data);
  
        /* Call pairWiseSwap() for rest of the list */
        pairWiseSwap(head.next.next);
    }
}
  
  
// This code contributed by aashish1995

JavaScript

<script>
/* Recursive function to pairwise swap elements
   of a linked list */
  
function pairWiseSwap(head)
{
    /* There must be at-least two nodes in the list */
    if (head != null && head.next != null) {
   
        /* Swap the node's data with data of next node */
        swap(head.data, head.next.data);
   
        /* Call pairWiseSwap() for rest of the list */
        pairWiseSwap(head.next.next);
    }
}
  
  
  
  
// This code is contributed by avanitrachhadiya2155
  
</script>

Complejidad temporal: O(n)

Espacio Auxiliar: O(1)

Como es una función recursiva de cola, la pila de llamadas de función no se construiría y, por lo tanto, no se usará espacio adicional.

La solución provista aquí intercambia datos de Nodes. Si los datos contienen muchos campos (por ejemplo, una lista enlazada de Objetos de Estudiante), la operación de intercambio será costosa. Consulte el siguiente artículo para obtener una mejor solución que funcione bien para todo tipo de listas vinculadas

Intercambiar Nodes por parejas cambiando enlaces

Escriba comentarios si encuentra algún error en el código/algoritmo anterior, o encuentre otras formas de resolver el mismo problema.

Publicación traducida automáticamente

Artículo escrito por GeeksforGeeks-1 y traducido por Barcelona Geeks. The original can be accessed here. Licence: CCBY-SA

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