Combinar dos listas enlazadas no ordenadas para obtener una lista ordenada – Part 1

Dadas dos listas enlazadas no ordenadas , la tarea es fusionarlas para obtener una lista enlazada individual ordenada .
Ejemplos: 

Entrada: Lista 1 = 3 -> 1 -> 5, Lista 2 = 6-> 2 -> 4 
Salida: 1 -> 2 -> 3 -> 4 -> 5 -> 6

Entrada: Lista 1 = 4 -> 7 -> 5, Lista 2 = 2-> 1 -> 8 -> 1 
Salida: 1 -> 1 -> 2 -> 4 -> 5 -> 7 -> 8 
 

Enfoque ingenuo: el enfoque ingenuo es ordenar las listas vinculadas dadas y luego fusionar las dos listas vinculadas ordenadas en una sola lista en orden creciente.
Para resolver el problema mencionado anteriormente, el método ingenuo es ordenar las dos listas vinculadas individualmente y fusionar las dos listas vinculadas en una sola lista que está en orden creciente.

Enfoque eficiente: para optimizar el método anterior, concatenaremos las dos listas vinculadas y luego las ordenaremos usando cualquier algoritmo de clasificación. A continuación se muestran los pasos: 

  1. Concatene las dos listas atravesando la primera lista hasta que lleguemos a su Node final y luego apunte el siguiente Node final al Node principal de la segunda lista. Almacene esta lista concatenada en la primera lista.
  2. Ordene la lista vinculada combinada anteriormente. Aquí, usaremos una ordenación de burbuja. Entonces, si el Node->siguiente->datos es menor que el Node->datos, entonces intercambie los datos de los dos Nodes adyacentes.

A continuación se muestra la implementación del enfoque anterior:

C++

// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;
 
// Create structure for a node
struct node {
    int data;
    node* next;
};
 
// Function to print the linked list
void setData(node* head)
{
    node* tmp;
 
    // Store the head of the linked
    // list into a temporary node*
    // and iterate
    tmp = head;
 
    while (tmp != NULL) {
 
        cout << tmp->data
             << " -> ";
        tmp = tmp->next;
    }
}
 
// Function takes the head of the
// LinkedList and the data as
// argument and if no LinkedList
// exists, it creates one with the
// head pointing to first node.
// If it exists already, it appends
// given node at end of the last node
node* getData(node* head, int num)
{
 
    // Create a new node
    node* temp = new node;
    node* tail = head;
 
    // Insert data into the temporary
    // node and point it's next to NULL
    temp->data = num;
    temp->next = NULL;
 
    // Check if head is null, create a
    // linked list with temp as head
    // and tail of the list
    if (head == NULL) {
        head = temp;
        tail = temp;
    }
 
    // Else insert the temporary node
    // after the tail of the existing
    // node and make the temporary node
    // as the tail of the linked list
    else {
 
        while (tail != NULL) {
 
            if (tail->next == NULL) {
                tail->next = temp;
                tail = tail->next;
            }
            tail = tail->next;
        }
    }
 
    // Return the list
    return head;
}
 
// Function to concatenate the two lists
node* mergelists(node** head1,
                 node** head2)
{
 
    node* tail = *head1;
 
    // Iterate through the head1 to find the
    // last node join the next of last node
    // of head1 to the 1st node of head2
    while (tail != NULL) {
 
        if (tail->next == NULL
            && head2 != NULL) {
            tail->next = *head2;
            break;
        }
        tail = tail->next;
    }
 
    // return the concatenated lists as a
    // single list - head1
    return *head1;
}
 
// Sort the linked list using bubble sort
void sortlist(node** head1)
{
    node* curr = *head1;
    node* temp = *head1;
 
    // Compares two adjacent elements
    // and swaps if the first element
    // is greater than the other one.
    while (curr->next != NULL) {
 
        temp = curr->next;
        while (temp != NULL) {
 
            if (temp->data < curr->data) {
                int t = temp->data;
                temp->data = curr->data;
                curr->data = t;
            }
            temp = temp->next;
        }
        curr = curr->next;
    }
}
 
// Driver Code
int main()
{
    node* head1 = new node;
    node* head2 = new node;
 
    head1 = NULL;
    head2 = NULL;
 
    // Given Linked List 1
    head1 = getData(head1, 4);
    head1 = getData(head1, 7);
    head1 = getData(head1, 5);
 
    // Given Linked List 2
    head2 = getData(head2, 2);
    head2 = getData(head2, 1);
    head2 = getData(head2, 8);
    head2 = getData(head2, 1);
 
    // Merge the two lists
    // in a single list
    head1 = mergelists(&head1,
                       &head2);
 
    // Sort the unsorted merged list
    sortlist(&head1);
 
    // Print the final
    // sorted merged list
    setData(head1);
    return 0;
}

Java

// Java program for
// the above approach
class GFG{
 
static node head1 = null;
static node head2 = null;
   
// Create structure for a node
static class node
{
  int data;
  node next;
};
 
// Function to print
// the linked list
static void setData(node head)
{
  node tmp;
   
  // Store the head of the linked
  // list into a temporary node
  // and iterate
  tmp = head;
 
  while (tmp != null)
  {
    System.out.print(tmp.data + " -> ");
    tmp = tmp.next;
  }
}
 
// Function takes the head of the
// LinkedList and the data as
// argument and if no LinkedList
// exists, it creates one with the
// head pointing to first node.
// If it exists already, it appends
// given node at end of the last node
static node getData(node head, int num)
{
  // Create a new node
  node temp = new node();
  node tail = head;
 
  // Insert data into the temporary
  // node and point it's next to null
  temp.data = num;
  temp.next = null;
 
  // Check if head is null, create a
  // linked list with temp as head
  // and tail of the list
  if (head == null)
  {
    head = temp;
    tail = temp;
  }
 
  // Else insert the temporary node
  // after the tail of the existing
  // node and make the temporary node
  // as the tail of the linked list
  else
  {
    while (tail != null)
    {
      if (tail.next == null)
      {
        tail.next = temp;
        tail = tail.next;
      }
      tail = tail.next;
    }
  }
 
  // Return the list
  return head;
}
 
// Function to concatenate
// the two lists
static node mergelists()
{
  node tail = head1;
 
  // Iterate through the
  // head1 to find the
  // last node join the
  // next of last node
  // of head1 to the
  // 1st node of head2
  while (tail != null)
  {
    if (tail.next == null &&
        head2 != null)
    {
      tail.next = head2;
      break;
    }
    tail = tail.next;
  }
 
  // return the concatenated
  // lists as a single list - head1
  return head1;
}
 
// Sort the linked list
// using bubble sort
static void sortlist()
{
  node curr = head1;
  node temp = head1;
 
  // Compares two adjacent elements
  // and swaps if the first element
  // is greater than the other one.
  while (curr.next != null)
  {
    temp = curr.next;
    while (temp != null)
    {
      if (temp.data < curr.data)
      {
        int t = temp.data;
        temp.data = curr.data;
        curr.data = t;
      }
      temp = temp.next;
    }
    curr = curr.next;
  }
}
 
// Driver Code
public static void main(String[] args)
{
  // Given Linked List 1
  head1 = getData(head1, 4);
  head1 = getData(head1, 7);
  head1 = getData(head1, 5);
 
  // Given Linked List 2
  head2 = getData(head2, 2);
  head2 = getData(head2, 1);
  head2 = getData(head2, 8);
  head2 = getData(head2, 1);
 
  // Merge the two lists
  // in a single list
  head1 = mergelists();
 
  // Sort the unsorted merged list
  sortlist();
 
  // Print the final
  // sorted merged list
  setData(head1);
}
}
 
// This code is contributed by shikhasingrajput

Python3

# Python3 program for the
# above approach
 
# Create structure for a node
class node:
   
    def __init__(self, x):
       
        self.data = x
        self.next = None
 
# Function to print the linked
# list
def setData(head):
 
    # Store the head of the
    # linked list into a
    # temporary node* and
    # iterate
    tmp = head
 
    while (tmp != None):
        print(tmp.data,
              end = " -> ")
        tmp = tmp.next
 
# Function takes the head of the
# LinkedList and the data as
# argument and if no LinkedList
# exists, it creates one with the
# head pointing to first node.
# If it exists already, it appends
# given node at end of the last node
def getData(head, num):
 
    # Create a new node
    temp = node(-1)
    tail = head
 
    # Insert data into the temporary
    # node and point it's next to NULL
    temp.data = num
    temp.next = None
 
    # Check if head is null, create a
    # linked list with temp as head
    # and tail of the list
    if (head == None):
        head = temp
        tail = temp
 
    # Else insert the temporary node
    # after the tail of the existing
    # node and make the temporary node
    # as the tail of the linked list
    else:
        while (tail != None):
            if (tail.next == None):
                tail.next = temp
                tail = tail.next
            tail = tail.next
 
    # Return the list
    return head
 
# Function to concatenate the
# two lists
def mergelists(head1,head2):
 
    tail = head1
 
    # Iterate through the head1 to
    # find the last node join the
    # next of last node of head1
    # to the 1st node of head2
    while (tail != None):
        if (tail.next == None
            and head2 != None):
            tail.next =head2
            break
        tail = tail.next
 
    # return the concatenated
    # lists as a single list
    # - head1
    return head1
 
# Sort the linked list using
# bubble sort
def sortlist(head1):
   
    curr = head1
    temp = head1
 
    # Compares two adjacent elements
    # and swaps if the first element
    # is greater than the other one.
    while (curr.next != None):
        temp = curr.next
        while (temp != None):
            if (temp.data < curr.data):
                t = temp.data
                temp.data = curr.data
                curr.data = t
            temp = temp.next
        curr = curr.next
 
# Driver Code
if __name__ == '__main__':
   
    head1 = node(-1)
    head2 = node(-1)
 
    head1 = None
    head2 = None
 
    # Given Linked List 1
    head1 = getData(head1, 4)
    head1 = getData(head1, 7)
    head1 = getData(head1, 5)
 
    # Given Linked List 2
    head2 = getData(head2, 2)
    head2 = getData(head2, 1)
    head2 = getData(head2, 8)
    head2 = getData(head2, 1)
 
    # Merge the two lists
    # in a single list
    head1 = mergelists(head1,head2)
 
    # Sort the unsorted merged list
    sortlist(head1)
 
    # Print the final
    # sorted merged list
    setData(head1)
 
# This code is contributed by Mohit Kumar 29

C#

// C# program for
// the above approach
using System;
 
class GFG{
 
static node head1 = null;
static node head2 = null;
   
// Create structure for a node
class node
{
    public int data;
    public node next;
};
 
// Function to print
// the linked list
static void setData(node head)
{
    node tmp;
     
    // Store the head of the linked
    // list into a temporary node
    // and iterate
    tmp = head;
     
    while (tmp != null)
    {
        Console.Write(tmp.data + " -> ");
        tmp = tmp.next;
    }
}
 
// Function takes the head of
//the List and the data as
// argument and if no List
// exists, it creates one with the
// head pointing to first node.
// If it exists already, it appends
// given node at end of the last node
static node getData(node head, int num)
{
     
    // Create a new node
    node temp = new node();
    node tail = head;
     
    // Insert data into the temporary
    // node and point it's next to null
    temp.data = num;
    temp.next = null;
     
    // Check if head is null, create a
    // linked list with temp as head
    // and tail of the list
    if (head == null)
    {
        head = temp;
        tail = temp;
    }
     
    // Else insert the temporary node
    // after the tail of the existing
    // node and make the temporary node
    // as the tail of the linked list
    else
    {
        while (tail != null)
        {
            if (tail.next == null)
            {
                tail.next = temp;
                tail = tail.next;
            }
            tail = tail.next;
        }
    }
     
    // Return the list
    return head;
}
 
// Function to concatenate
// the two lists
static node mergelists()
{
    node tail = head1;
     
    // Iterate through the
    // head1 to find the
    // last node join the
    // next of last node
    // of head1 to the
    // 1st node of head2
    while (tail != null)
    {
        if (tail.next == null &&
                head2 != null)
        {
            tail.next = head2;
            break;
        }
        tail = tail.next;
    }
     
    // return the concatenated
    // lists as a single list - head1
    return head1;
}
 
// Sort the linked list
// using bubble sort
static void sortlist()
{
    node curr = head1;
    node temp = head1;
     
    // Compares two adjacent elements
    // and swaps if the first element
    // is greater than the other one.
    while (curr.next != null)
    {
        temp = curr.next;
        while (temp != null)
        {
            if (temp.data < curr.data)
            {
                int t = temp.data;
                temp.data = curr.data;
                curr.data = t;
            }
            temp = temp.next;
        }
        curr = curr.next;
    }
}
 
// Driver Code
public static void Main(String[] args)
{
     
    // Given Linked List 1
    head1 = getData(head1, 4);
    head1 = getData(head1, 7);
    head1 = getData(head1, 5);
     
    // Given Linked List 2
    head2 = getData(head2, 2);
    head2 = getData(head2, 1);
    head2 = getData(head2, 8);
    head2 = getData(head2, 1);
     
    // Merge the two lists
    // in a single list
    head1 = mergelists();
     
    // Sort the unsorted merged list
    sortlist();
     
    // Print the final
    // sorted merged list
    setData(head1);
}
}
 
// This code is contributed by Amit Katiyar

Javascript

<script>
// javascript program for
// the above approach   
    var head1 = null;
    var head2 = null;
 
    // Create structure for a node
    class node {
    constructor(){
         this.data=0;
         this.next = null;
        }
    }
 
    // Function to print
    // the linked list
    function setData( head) {
        var tmp;
 
        // Store the head of the linked
        // list into a temporary node
        // and iterate
        tmp = head;
 
        while (tmp != null) {
            document.write(tmp.data + " -> ");
            tmp = tmp.next;
        }
    }
 
    // Function takes the head of the
    // LinkedList and the data as
    // argument and if no LinkedList
    // exists, it creates one with the
    // head pointing to first node.
    // If it exists already, it appends
    // given node at end of the last node
    function getData( head , num) {
        // Create a new node
         temp = new node();
        var tail = head;
 
        // Insert data into the temporary
        // node and point it's next to null
        temp.data = num;
        temp.next = null;
 
        // Check if head is null, create a
        // linked list with temp as head
        // and tail of the list
        if (head == null) {
            head = temp;
            tail = temp;
        }
 
        // Else insert the temporary node
        // after the tail of the existing
        // node and make the temporary node
        // as the tail of the linked list
        else {
            while (tail != null) {
                if (tail.next == null) {
                    tail.next = temp;
                    tail = tail.next;
                }
                tail = tail.next;
            }
        }
 
        // Return the list
        return head;
    }
 
    // Function to concatenate
    // the two lists
    function mergelists() {
         tail = head1;
 
        // Iterate through the
        // head1 to find the
        // last node join the
        // next of last node
        // of head1 to the
        // 1st node of head2
        while (tail != null) {
            if (tail.next == null && head2 != null) {
                tail.next = head2;
                break;
            }
            tail = tail.next;
        }
 
        // return the concatenated
        // lists as a single list - head1
        return head1;
    }
 
    // Sort the linked list
    // using bubble sort
    function sortlist() {
         curr = head1;
         temp = head1;
 
        // Compares two adjacent elements
        // and swaps if the first element
        // is greater than the other one.
        while (curr.next != null) {
            temp = curr.next;
            while (temp != null) {
                if (temp.data < curr.data) {
                    var t = temp.data;
                    temp.data = curr.data;
                    curr.data = t;
                }
                temp = temp.next;
            }
            curr = curr.next;
        }
    }
 
    // Driver Code
     
        // Given Linked List 1
        head1 = getData(head1, 4);
        head1 = getData(head1, 7);
        head1 = getData(head1, 5);
 
        // Given Linked List 2
        head2 = getData(head2, 2);
        head2 = getData(head2, 1);
        head2 = getData(head2, 8);
        head2 = getData(head2, 1);
 
        // Merge the two lists
        // in a single list
        head1 = mergelists();
 
        // Sort the unsorted merged list
        sortlist();
 
        // Print the final
        // sorted merged list
        setData(head1);
 
// This code is contributed by umadevi9616.
</script>
Producción: 

1 -> 1 -> 2 -> 4 -> 5 -> 7 -> 8

 

Complejidad de tiempo: O ((M + N) ^ 2) donde M y N son las longitudes de las dos listas vinculadas dadas. Estamos fusionando las dos listas y realizando una ordenación de burbujas en la lista fusionada. La complejidad temporal del tipo de burbuja es cuadrática.
Espacio Auxiliar : O(1)

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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