Combinar dos listas enlazadas ordenadas – Part 1

Escriba una función SortedMerge() que tome dos listas, cada una de las cuales está ordenada en orden creciente, y fusione las dos en una lista en orden creciente. SortedMerge() debería devolver la nueva lista. La nueva lista debe hacerse empalmando los Nodes de las dos primeras listas.

Por ejemplo, si la primera lista enlazada a es 5->10->15 y la otra lista enlazada b es 2->3->20, SortedMerge() debería devolver un puntero al Node principal de la lista fusionada 2-> 3->5->10->15->20.

C++

/* C++ program to merge two sorted linked lists */
#include <bits/stdc++.h>
using namespace std;
  
/* Link list node */
class Node 
{ 
    public:
    int data; 
    Node* next; 
}; 
  
/* pull off the front node of 
the source and put it in dest */
void MoveNode(Node** destRef, Node** sourceRef); 
  
/* Takes two lists sorted in increasing
order, and splices their nodes together
to make one big sorted list which 
is returned. */
Node* SortedMerge(Node* a, Node* b) 
{ 
    /* a dummy first node to hang the result on */
    Node dummy; 
  
    /* tail points to the last result node */
    Node* tail = &dummy; 
  
    /* so tail->next is the place to  
    add new nodes to the result. */
    dummy.next = NULL; 
    while (1) 
    { 
        if (a == NULL) 
        { 
            /* if either list runs out, use the 
            other list */
            tail->next = b; 
            break; 
        } 
        else if (b == NULL) 
        { 
            tail->next = a; 
            break; 
        } 
        if (a->data <= b->data) 
            MoveNode(&(tail->next), &a); 
        else
            MoveNode(&(tail->next), &b); 
  
        tail = tail->next; 
    } 
    return(dummy.next); 
} 
  
/* UTILITY FUNCTIONS */
/* MoveNode() function takes the
node from the front of the source,
and move it to the front of the dest. 
It is an error to call this with the 
source list empty. 
  
Before calling MoveNode(): 
source == {1, 2, 3} 
dest == {1, 2, 3} 
  
After calling MoveNode(): 
source == {2, 3} 
dest == {1, 1, 2, 3} */
void MoveNode(Node** destRef, Node** sourceRef) 
{ 
    /* the front source node */
    Node* newNode = *sourceRef; 
    assert(newNode != NULL); 
  
    /* Advance the source pointer */
    *sourceRef = newNode->next; 
  
    /* Link the old dest off the new node */
    newNode->next = *destRef; 
  
    /* Move dest to point to the new node */
    *destRef = newNode; 
} 
  
  
/* Function to insert a node at  
the beginning of the 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() 
{ 
    /* Start with the empty list */
    Node* res = NULL; 
    Node* a = NULL; 
    Node* b = NULL; 
  
    /* Let us create two sorted linked lists  
    to test the functions 
    Created lists, a: 5->10->15, b: 2->3->20 */
    push(&a, 15); 
    push(&a, 10); 
    push(&a, 5); 
  
    push(&b, 20); 
    push(&b, 3); 
    push(&b, 2); 
  
    /* Remove duplicates from linked list */
    res = SortedMerge(a, b); 
  
    cout << "Merged Linked List is: \n"; 
    printList(res); 
  
    return 0; 
} 
  
// This code is contributed by rathbhupendra

C

/* C program to merge two sorted linked lists */
#include<stdio.h>
#include<stdlib.h>
#include<assert.h>
  
/* Link list node */
struct Node
{
    int data;
    struct Node* next;
};
  
/* pull off the front node of the source and put it in dest */
void MoveNode(struct Node** destRef, struct Node** sourceRef);
  
/* Takes two lists sorted in increasing order, and splices
   their nodes together to make one big sorted list which
   is returned.  */
struct Node* SortedMerge(struct Node* a, struct Node* b)
{
    /* a dummy first node to hang the result on */
    struct Node dummy;
  
    /* tail points to the last result node  */
    struct Node* tail = &dummy;
  
    /* so tail->next is the place to add new nodes
      to the result. */
    dummy.next = NULL;
    while (1)
    {
        if (a == NULL)
        {
            /* if either list runs out, use the
               other list */
            tail->next = b;
            break;
        }
        else if (b == NULL)
        {
            tail->next = a;
            break;
        }
        if (a->data <= b->data)
            MoveNode(&(tail->next), &a);
        else
            MoveNode(&(tail->next), &b);
  
        tail = tail->next;
    }
    return(dummy.next);
}
  
/* UTILITY FUNCTIONS */
/* MoveNode() function takes the node from the front of the
   source, and move it to the front of the dest.
   It is an error to call this with the source list empty.
  
   Before calling MoveNode():
   source == {1, 2, 3}
   dest == {1, 2, 3}
  
   After calling MoveNode():
   source == {2, 3}
   dest == {1, 1, 2, 3} */
void MoveNode(struct Node** destRef, struct Node** sourceRef)
{
    /* the front source node  */
    struct Node* newNode = *sourceRef;
    assert(newNode != NULL);
  
    /* Advance the source pointer */
    *sourceRef = newNode->next;
  
    /* Link the old dest off the new node */
    newNode->next = *destRef;
  
    /* Move dest to point to the new node */
    *destRef = newNode;
}
  
  
/* Function to insert a node at the beginning of the
   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 functions*/
int main()
{
    /* Start with the empty list */
    struct Node* res = NULL;
    struct Node* a = NULL;
    struct Node* b = NULL;
  
    /* Let us create two sorted linked lists to test
      the functions
       Created lists, a: 5->10->15,  b: 2->3->20 */
    push(&a, 15);
    push(&a, 10);
    push(&a, 5);
  
    push(&b, 20);
    push(&b, 3);
    push(&b, 2);
  
    /* Remove duplicates from linked list */
    res = SortedMerge(a, b);
  
    printf("Merged Linked List is: \n");
    printList(res);
  
    return 0;
}

Java

/* Java program to merge two
   sorted linked lists */
import java.util.*;
  
/* Link list node */
class Node 
{
    int data;
    Node next;
    Node(int d) {data = d;
                 next = null;}
}
      
class MergeLists 
{
Node head; 
  
/* Method to insert a node at 
   the end of the linked list */
public void addToTheLast(Node node) 
{
    if (head == null)
    {
        head = node;
    }
    else 
    {
        Node temp = head;
        while (temp.next != null)
            temp = temp.next;
        temp.next = node;
    }
}
  
/* Method to print linked list */
void printList()
{
    Node temp = head;
    while (temp != null)
    {
        System.out.print(temp.data + " ");
        temp = temp.next;
    } 
    System.out.println();
}
  
  
// Driver Code
public static void main(String args[])
{
    /* Let us create two sorted linked
       lists to test the methods 
       Created lists:
           llist1: 5->10->15,
           llist2: 2->3->20
    */
    MergeLists llist1 = new MergeLists();
    MergeLists llist2 = new MergeLists();
      
    // Node head1 = new Node(5);
    llist1.addToTheLast(new Node(5));
    llist1.addToTheLast(new Node(10));
    llist1.addToTheLast(new Node(15));
      
    // Node head2 = new Node(2);
    llist2.addToTheLast(new Node(2));
    llist2.addToTheLast(new Node(3));
    llist2.addToTheLast(new Node(20));
      
      
    llist1.head = new Gfg().sortedMerge(llist1.head, 
                                        llist2.head);
    llist1.printList();     
      
}
}
  
class Gfg
{
/* Takes two lists sorted in 
increasing order, and splices 
their nodes together to make 
one big sorted list which is 
returned. */
Node sortedMerge(Node headA, Node headB)
{
      
    /* a dummy first node to 
       hang the result on */
    Node dummyNode = new Node(0);
      
    /* tail points to the 
    last result node */
    Node tail = dummyNode;
    while(true) 
    {
          
        /* if either list runs out, 
        use the other list */
        if(headA == null)
        {
            tail.next = headB;
            break;
        }
        if(headB == null)
        {
            tail.next = headA;
            break;
        }
          
        /* Compare the data of the two
        lists whichever lists' data is 
        smaller, append it into tail and
        advance the head to the next Node
        */
        if(headA.data <= headB.data)
        {
            tail.next = headA;
            headA = headA.next;
        } 
        else
        {
            tail.next = headB;
            headB = headB.next;
        }
          
        /* Advance the tail */
        tail = tail.next;
    }
    return dummyNode.next;
}
}
  
// This code is contributed
// by Shubhaw Kumar

Python3

""" Python program to merge two
sorted linked lists """
  
  
# Linked List Node
class Node:
    def __init__(self, data):
        self.data = data
        self.next = None
  
  
# Create & Handle List operations
class LinkedList:
    def __init__(self):
        self.head = None
  
    # Method to display the list
    def printList(self):
        temp = self.head
        while temp:
            print(temp.data, end=" ")
            temp = temp.next
  
    # Method to add element to list
    def addToList(self, newData):
        newNode = Node(newData)
        if self.head is None:
            self.head = newNode
            return
  
        last = self.head
        while last.next:
            last = last.next
  
        last.next = newNode
  
  
# Function to merge the lists
# Takes two lists which are sorted
# joins them to get a single sorted list
def mergeLists(headA, headB):
  
    # A dummy node to store the result
    dummyNode = Node(0)
  
    # Tail stores the last node
    tail = dummyNode
    while True:
  
        # If any of the list gets completely empty
        # directly join all the elements of the other list
        if headA is None:
            tail.next = headB
            break
        if headB is None:
            tail.next = headA
            break
  
        # Compare the data of the lists and whichever is smaller is
        # appended to the last of the merged list and the head is changed
        if headA.data <= headB.data:
            tail.next = headA
            headA = headA.next
        else:
            tail.next = headB
            headB = headB.next
  
        # Advance the tail
        tail = tail.next
  
    # Returns the head of the merged list
    return dummyNode.next
  
  
# Create 2 lists
listA = LinkedList()
listB = LinkedList()
  
# Add elements to the list in sorted order
listA.addToList(5)
listA.addToList(10)
listA.addToList(15)
  
listB.addToList(2)
listB.addToList(3)
listB.addToList(20)
  
# Call the merge function
listA.head = mergeLists(listA.head, listB.head)
  
# Display merged list
print("Merged Linked List is:")
listA.printList()
  
""" This code is contributed
by Debidutta Rath """

C#

/* C# program to merge two 
sorted linked lists */
using System;
  
    /* Link list node */
    public class Node 
    { 
        public int data; 
        public Node next; 
        public Node(int d) 
        {
            data = d; 
            next = null;
        } 
    } 
  
    public class MergeLists 
    { 
        Node head; 
  
        /* Method to insert a node at 
        the end of the linked list */
        public void addToTheLast(Node node) 
        { 
            if (head == null) 
            { 
                head = node; 
            } 
            else
            { 
                Node temp = head; 
                while (temp.next != null) 
                    temp = temp.next; 
                temp.next = node; 
            } 
        } 
  
        /* Method to print linked list */
        void printList() 
        { 
            Node temp = head; 
            while (temp != null) 
            { 
                   Console.Write(temp.data + " "); 
                temp = temp.next; 
            } 
            Console.WriteLine(); 
        } 
  
  
        // Driver Code 
        public static void Main(String []args) 
        { 
            /* Let us create two sorted linked 
            lists to test the methods 
            Created lists: 
                   llist1: 5->10->15, 
                llist2: 2->3->20 
            */
            MergeLists llist1 = new MergeLists(); 
            MergeLists llist2 = new MergeLists(); 
  
            // Node head1 = new Node(5); 
            llist1.addToTheLast(new Node(5)); 
            llist1.addToTheLast(new Node(10)); 
            llist1.addToTheLast(new Node(15)); 
  
            // Node head2 = new Node(2); 
            llist2.addToTheLast(new Node(2)); 
            llist2.addToTheLast(new Node(3)); 
            llist2.addToTheLast(new Node(20)); 
  
  
            llist1.head = new Gfg().sortedMerge(llist1.head, 
                                            llist2.head); 
            llist1.printList(); 
  
        } 
    } 
  
    public class Gfg 
    { 
    /* Takes two lists sorted in 
    increasing order, and splices 
    their nodes together to make 
    one big sorted list which is 
    returned. */
    public Node sortedMerge(Node headA, Node headB) 
    { 
  
        /* a dummy first node to 
        hang the result on */
        Node dummyNode = new Node(0); 
  
        /* tail points to the 
        last result node */
        Node tail = dummyNode; 
        while(true) 
        { 
  
            /* if either list runs out, 
            use the other list */
            if(headA == null) 
            { 
                tail.next = headB; 
                break; 
            } 
            if(headB == null) 
            { 
                tail.next = headA; 
                break; 
            } 
  
            /* Compare the data of the two 
            lists whichever lists' data is 
            smaller, append it into tail and 
            advance the head to the next Node 
            */
            if(headA.data <= headB.data) 
            { 
                tail.next = headA; 
                headA = headA.next; 
            } 
            else
            { 
                tail.next = headB; 
                headB = headB.next; 
            } 
  
            /* Advance the tail */
            tail = tail.next; 
        } 
        return dummyNode.next; 
    } 
} 
  
// This code is contributed 29AjayKumar

Javascript

<script>
  
class Node
{
    constructor(d)
    {
        this.data=d;
        this.next = null;
    }
}
  
class LinkedList
{
  
constructor()
{
    this.head=null;
}
  
  
addToTheLast(node)
{
    if (this.head == null)
    {
        this.head = node;
    }
    else
    {
        let temp = this.head;
        while (temp.next != null)
            temp = temp.next;
        temp.next = node;
    }
}
  
printList()
{
    let temp = this.head;
    while (temp != null)
    {
        document.write(temp.data + " ");
        temp = temp.next;
    }
    document.write("<br>");
}
}
  
function sortedMerge(headA,headB)
{
    /* a dummy first node to
       hang the result on */
    let dummyNode = new Node(0);
       
    /* tail points to the
    last result node */
    let tail = dummyNode;
    while(true)
    {
           
        /* if either list runs out,
        use the other list */
        if(headA == null)
        {
            tail.next = headB;
            break;
        }
        if(headB == null)
        {
            tail.next = headA;
            break;
        }
           
        /* Compare the data of the two
        lists whichever lists' data is
        smaller, append it into tail and
        advance the head to the next Node
        */
        if(headA.data <= headB.data)
        {
            tail.next = headA;
            headA = headA.next;
        }
        else
        {
            tail.next = headB;
            headB = headB.next;
        }
           
        /* Advance the tail */
        tail = tail.next;
    }
    return dummyNode.next;
}
  
  
/* Let us create two sorted linked
       lists to test the methods
       Created lists:
           llist1: 5->10->15,
           llist2: 2->3->20
    */
let llist1 = new LinkedList();
let llist2 = new LinkedList();
  
// Node head1 = new Node(5);
llist1.addToTheLast(new Node(5));
llist1.addToTheLast(new Node(10));
llist1.addToTheLast(new Node(15));
  
// Node head2 = new Node(2);
llist2.addToTheLast(new Node(2));
llist2.addToTheLast(new Node(3));
llist2.addToTheLast(new Node(20));
  
  
llist1.head = sortedMerge(llist1.head,
                                    llist2.head);
document.write("Merged Linked List is:<br>")
llist1.printList();    
  
// This code is contributed by patel2127
</script>

C++14

Node* SortedMerge(Node* a, Node* b)
{
    Node* result = NULL;
  
    /* point to the last result pointer */
    Node** lastPtrRef = &result;
  
    while (1) {
        if (a == NULL) {
            *lastPtrRef = b;
            break;
        }
        else if (b == NULL) {
            *lastPtrRef = a;
            break;
        }
        if (a->data <= b->data)
            MoveNode(lastPtrRef, &a);
        else
            MoveNode(lastPtrRef, &b);
  
        /* tricky: advance to point to the next ".next"
         * field */
        lastPtrRef = &((*lastPtrRef)->next);
    }
    return (result);
}
  
// This code is contributed by Aditya Kumar (adityakumar129)

C

struct Node* SortedMerge(struct Node* a, struct Node* b)
{
    struct Node* result = NULL;
  
    /* point to the last result pointer */
    struct Node** lastPtrRef = &result;
  
    while (1) {
        if (a == NULL) {
            *lastPtrRef = b;
            break;
        }
        else if (b == NULL) {
            *lastPtrRef = a;
            break;
        }
        if (a->data <= b->data)
            MoveNode(lastPtrRef, &a);
        else
            MoveNode(lastPtrRef, &b);
  
        /* tricky: advance to point to the next ".next"
         * field */
        lastPtrRef = &((*lastPtrRef)->next);
    }
    return (result);
}
  
// This code is contributed by Aditya Kumar (adityakumar129)

Java

Node SortedMerge(Node a, Node b)
{
    Node result = null;
  
    /* point to the last result pointer */
    Node lastPtrRef = result;
  
    while (1) {
        if (a == null) {
            lastPtrRef = b;
            break;
        }
        else if (b == null) {
            lastPtrRef = a;
            break;
        }
        if (a.data <= b.data)
            MoveNode(lastPtrRef, a);
        else
            MoveNode(lastPtrRef, b);
  
        /* tricky: advance to point to the next ".next"
         * field */
        lastPtrRef = ((lastPtrRef).next);
    }
    return (result);
}
  
// This code is contributed by Aditya Kumar (adityakumar129)

Python3

def SortedMerge( a,  b):
    result = None; 
          
    ''' point to the last result pointer '''
    lastPtrRef = result; 
          
    while(1):
        if (a == None):
            lastPtrRef = b; 
            break; 
        elif(b == None): 
            lastPtrRef = a; 
            break; 
        if(a.data <= b.data): 
            MoveNode(lastPtrRef, a); 
        else: 
            MoveNode(lastPtrRef, b); 
  
        ''' tricky: advance to point to the next ".next" field '''
        lastPtrRef = ((lastPtrRef).next); 
    return(result); 
    
 # This code is contributed by umadevi9616 

C#

Node SortedMerge(Node a, Node b)
{
    Node result = null;
  
    // Point to the last result pointer
    Node lastPtrRef = result;
  
    while (1) {
        if (a == null) {
            lastPtrRef = b;
            break;
        }
        else if (b == null) {
            lastPtrRef = a;
            break;
        }
        if (a.data <= b.data)
            MoveNode(lastPtrRef, a);
        else
            MoveNode(lastPtrRef, b);
  
        // tricky: advance to point to
        // the next ".next" field
        lastPtrRef = ((lastPtrRef).next);
    }
    return (result);
}
  
// This code is contributed by gauravrajput1

Javascript

<script>
  
function SortedMerge(a,b)
{
    let result = null;
       
/* point to the last result pointer */
let lastPtrRef = result;
       
while(1)
{
    if (a == null)
    {
    lastPtrRef = b;
    break;
    }
    else if (b==null)
    {
    lastPtrRef = a;
    break;
    }
    if(a.data <= b.data)
    {
    MoveNode(lastPtrRef, a);
    }
    else
    {
    MoveNode(lastPtrRef, b);
    }
       
    /* tricky: advance to point to the next ".next" field */
    lastPtrRef = ((lastPtrRef).next);
}
return(result);
}
      
  
// This code is contributed by rag2127
  
</script>

C++

Node* SortedMerge(Node* a, Node* b) 
{ 
    Node* result = NULL; 
      
    /* Base cases */
    if (a == NULL) 
        return(b); 
    else if (b == NULL) 
        return(a); 
      
    /* Pick either a or b, and recur */
    if (a->data <= b->data) 
    { 
        result = a; 
        result->next = SortedMerge(a->next, b); 
    } 
    else
    { 
        result = b; 
        result->next = SortedMerge(a, b->next); 
    } 
    return(result); 
} 
  
// This code is contributed by rathbhupendra

C

struct Node* SortedMerge(struct Node* a, struct Node* b) 
{
  struct Node* result = NULL;
  
  /* Base cases */
  if (a == NULL) 
     return(b);
  else if (b==NULL) 
     return(a);
  
  /* Pick either a or b, and recur */
  if (a->data <= b->data) 
  {
     result = a;
     result->next = SortedMerge(a->next, b);
  }
  else 
  {
     result = b;
     result->next = SortedMerge(a, b->next);
  }
  return(result);
}

Java

class GFG 
{
    public Node SortedMerge(Node A, Node B) 
    {
      
        if(A == null) return B;
        if(B == null) return A;
          
        if(A.data < B.data) 
        {
            A.next = SortedMerge(A.next, B);
            return A;
        }
        else 
        {
            B.next = SortedMerge(A, B.next);
            return B;
        }
          
    }
}
  
// This code is contributed by Tuhin Das

Python3

# Python3 program merge two sorted linked
# in third linked list using recursive.
  
# Node class
class Node:
    def __init__(self, data):
        self.data = data
        self.next = None
  
  
# Constructor to initialize the node object
class LinkedList:
  
    # Function to initialize head
    def __init__(self):
        self.head = None
  
    # Method to print linked list
    def printList(self):
        temp = self.head
          
        while temp :
            print(temp.data, end="->")
            temp = temp.next
  
    # Function to add of node at the end.
    def append(self, new_data):
        new_node = Node(new_data)
          
        if self.head is None:
            self.head = new_node
            return
        last = self.head
          
        while last.next:
            last = last.next
        last.next = new_node
  
  
# Function to merge two sorted linked list.
def mergeLists(head1, head2):
  
    # create a temp node NULL
    temp = None
  
    # List1 is empty then return List2
    if head1 is None:
        return head2
  
    # if List2 is empty then return List1
    if head2 is None:
        return head1
  
    # If List1's data is smaller or
    # equal to List2's data
    if head1.data <= head2.data:
  
        # assign temp to List1's data
        temp = head1
  
        # Again check List1's data is smaller or equal List2's 
        # data and call mergeLists function.
        temp.next = mergeLists(head1.next, head2)
          
    else:
        # If List2's data is greater than or equal List1's 
        # data assign temp to head2
        temp = head2
  
        # Again check List2's data is greater or equal List's
        # data and call mergeLists function.
        temp.next = mergeLists(head1, head2.next)
  
    # return the temp list.
    return temp
  
  
# Driver Function
if __name__ == '__main__':
  
    # Create linked list :
    # 10->20->30->40->50
    list1 = LinkedList()
    list1.append(10)
    list1.append(20)
    list1.append(30)
    list1.append(40)
    list1.append(50)
  
    # Create linked list 2 :
    # 5->15->18->35->60
    list2 = LinkedList()
    list2.append(5)
    list2.append(15)
    list2.append(18)
    list2.append(35)
    list2.append(60)
  
    # Create linked list 3
    list3 = LinkedList()
  
    # Merging linked list 1 and linked list 2
    # in linked list 3
    list3.head = mergeLists(list1.head, list2.head)
  
    print(" Merged Linked List is : ", end="")
    list3.printList()     
  
  
# This code is contributed by 'Shriaknt13'.         

C#

using System;
  
class GFG{
  
public Node sortedMerge(Node A, Node B) 
{
      
    // Base cases
    if (A == null)
        return B;
    if (B == null) 
        return A;
          
    // Pick either a or b, and recur 
    if (A.data < B.data) 
    {
        A.next = sortedMerge(A.next, B);
        return A;
    }
    else
    {
        B.next = sortedMerge(A, B.next);
        return B;
    }
}
}
  
// This code is contributed by hunter2000

Javascript

<script>
  
    function SortedMerge( A,  B) {
  
        if (A == null)
            return B;
        if (B == null)
            return A;
  
        if (A.data < B.data) {
            A.next = SortedMerge(A.next, B);
            return A;
        } else {
            B.next = SortedMerge(A, B.next);
            return B;
        }
  
    }
  
// This code contributed by umadevi9616 
</script>

C

/*Given two sorted linked lists consisting of N and M nodes
respectively. The task is to merge both of the list
(in-place) and return head of the merged list.*/
#include <stdio.h>
#include <stdlib.h>
  
/* Link list Node */
typedef struct Node {
    int key;
    struct Node* next;
}Node;
  
// Function to reverse a given Linked List using Recursion
Node* reverseList(Node* head)
{
    if (head->next == NULL)
        return head;
    Node* rest = reverseList(head->next);
    head->next->next = head;
    head->next = NULL;
    return rest;
}
  
// Given two non-empty linked lists 'a' and 'b'
Node* sortedMerge(Node* a, Node* b)
{
    // Reverse Linked List 'a'
    a = reverseList(a);
    // Reverse Linked List 'b'
    b = reverseList(b);
    // Initialize head of resultant list
    Node* head = NULL;
    Node* temp;
    // Traverse both lists while both of them
    // have nodes.
    while (a != NULL && b != NULL) {
        // If a's current value is greater than or equal to
        // b's current value.
        if (a->key >= b->key) {
            // Store next of current Node in first list
            temp = a->next;
            // Add 'a' at the front of resultant list
            a->next = head;
            // Make 'a' - head of the result list
            head = a;
            // Move ahead in first list
            a = temp;
        }
        
        // If b's value is greater. Below steps are similar
        // to above (Only 'a' is replaced with 'b')
        else {
            temp = b->next;
            b->next = head;
            head = b;
            b = temp;
        }
    }
  
    // If second list reached end, but first list has
    // nodes. Add remaining nodes of first list at the
    // beginning of result list
    while (a != NULL) {
        temp = a->next;
        a->next = head;
        head = a;
        a = temp;
    }
  
    // If first list reached end, but second list has
    // nodes. Add remaining nodes of second list at the
    // beginning of result list
    while (b != NULL) {
        temp = b->next;
        b->next = head;
        head = b;
        b = temp;
    }
    // Return the head of the result list
    return head;
}
  
/* Function to print Nodes in a given linked list */
void printList(struct Node* Node)
{
    while (Node != NULL) {
        printf("%d  ",Node->key);
        Node = Node->next;
    }
}
  
/* Utility function to create a new node with
   given key */
Node* newNode(int key)
{
    Node* temp = (Node *)malloc(sizeof(Node));
    temp->key = key;
    temp->next = NULL;
    return temp;
}
  
/* Driver program to test above functions*/
int main()
{
    /* Start with the empty list */
    struct Node* res = NULL;
    /* Let us create two sorted linked lists to test
       the above functions. Created lists shall be
         a: 5->10->15->40
         b: 2->3->20  */
    Node* a = newNode(5);
    a->next = newNode(10);
    a->next->next = newNode(15);
    a->next->next->next = newNode(40);
  
    Node* b = newNode(2);
    b->next = newNode(3);
    b->next->next = newNode(20);
  
    printf("List A before merge: \n");
    printList(a);
  
    printf("\nList B before merge: \n");
    printList(b);
  
    /* merge 2 sorted Linked Lists */
    res = sortedMerge(a, b);
  
    printf("\nMerged Linked List is: \n");
    printList(res);
  
    return 0;
}
  
// This code is contributed by Aditya Kumar (adityakumar129)

C++

/*Given two sorted linked lists consisting of N and M nodes
respectively. The task is to merge both of the list
(in-place) and return head of the merged list.*/
#include <iostream>
using namespace std;
  
/* Link list Node */
struct Node {
    int key;
    struct Node* next;
};
  
// Function to reverse a given Linked List using Recursion
Node* reverseList(Node* head)
{
    if (head->next == NULL)
        return head;
    Node* rest = reverseList(head->next);
    head->next->next = head;
    head->next = NULL;
    return rest;
}
  
// Given two non-empty linked lists 'a' and 'b'
Node* sortedMerge(Node* a, Node* b)
{
    // Reverse Linked List 'a'
    a = reverseList(a);
    // Reverse Linked List 'b'
    b = reverseList(b);
    // Initialize head of resultant list
    Node* head = NULL;
    Node* temp;
    // Traverse both lists while both of them
    // have nodes.
    while (a != NULL && b != NULL) {
        // If a's current value is greater than or equal to
        // b's current value.
        if (a->key >= b->key) {
            // Store next of current Node in first list
            temp = a->next;
            // Add 'a' at the front of resultant list
            a->next = head;
            // Make 'a' - head of the result list
            head = a;
            // Move ahead in first list
            a = temp;
        }
        
        // If b's value is greater. Below steps are similar
        // to above (Only 'a' is replaced with 'b')
        else {
            temp = b->next;
            b->next = head;
            head = b;
            b = temp;
        }
    }
  
    // If second list reached end, but first list has
    // nodes. Add remaining nodes of first list at the
    // beginning of result list
    while (a != NULL) {
        temp = a->next;
        a->next = head;
        head = a;
        a = temp;
    }
  
    // If first list reached end, but second list has
    // nodes. Add remaining nodes of second list at the
    // beginning of result list
    while (b != NULL) {
        temp = b->next;
        b->next = head;
        head = b;
        b = temp;
    }
    // Return the head of the result list
    return head;
}
  
/* Function to print Nodes in a given linked list */
void printList(struct Node* Node)
{
    while (Node != NULL) {
        cout << Node->key << " ";
        Node = Node->next;
    }
}
  
/* Utility function to create a new node with
   given key */
Node* newNode(int key)
{
    Node* temp = new Node;
    temp->key = key;
    temp->next = NULL;
    return temp;
}
  
/* Driver program to test above functions*/
int main()
{
    /* Start with the empty list */
    struct Node* res = NULL;
  
    /* Let us create two sorted linked lists to test
       the above functions. Created lists shall be
         a: 5->10->15->40
         b: 2->3->20  */
    Node* a = newNode(5);
    a->next = newNode(10);
    a->next->next = newNode(15);
    a->next->next->next = newNode(40);
  
    Node* b = newNode(2);
    b->next = newNode(3);
    b->next->next = newNode(20);
  
    cout << "List A before merge: \n";
    printList(a);
  
    cout << "\nList B before merge: \n";
    printList(b);
  
    /* merge 2 sorted Linked Lists */
    res = sortedMerge(a, b);
  
    cout << "\nMerged Linked List is: \n";
    printList(res);
  
    return 0;
}
  
// This code is contributed by Aditya Kumar (adityakumar129)

Java

/*Given two sorted linked lists consisting of N and M nodes
respectively. The task is to merge both of the list
(in-place) and return head of the merged list.*/
  
import java.util.*;
  
class GFG{
  
/* Link list Node */
static class Node {
    int key;
    Node next;
};
  
// Function to reverse a given Linked List using Recursion
static Node reverseList(Node head)
{
  
    if (head.next == null)
        return head;
  
    Node rest = reverseList(head.next);
    head.next.next = head;
    head.next = null;
  
    return rest;
}
  
// Given two non-empty linked lists 'a' and 'b'
static Node sortedMerge(Node a, Node b)
{
    
    // Reverse Linked List 'a'
    a = reverseList(a);
  
    // Reverse Linked List 'b'
    b = reverseList(b);
  
    // Initialize head of resultant list
    Node head = null;
  
    Node temp;
  
    // Traverse both lists while both of them
    // have nodes.
    while (a != null && b != null) {
  
        // If a's current value is greater than or equal to
        // b's current value.
        if (a.key >= b.key) {
  
            // Store next of current Node in first list
            temp = a.next;
            
            // Add 'a' at the front of resultant list
            a.next = head;
            
            // Make 'a' - head of the result list
            head = a;
            
            // Move ahead in first list
            a = temp;
        }
        
        // If b's value is greater. Below steps are similar
        // to above (Only 'a' is replaced with 'b')
        else {
  
            temp = b.next;
            b.next = head;
            head = b;
            b = temp;
        }
    }
  
    // If second list reached end, but first list has
    // nodes. Add remaining nodes of first list at the
    // beginning of result list
    while (a != null) {
  
        temp = a.next;
        a.next = head;
        head = a;
        a = temp;
    }
  
    // If first list reached end, but second list has
    // nodes. Add remaining nodes of second list at the
    // beginning of result list
    while (b != null) {
  
        temp = b.next;
        b.next = head;
        head = b;
        b = temp;
    }
  
    // Return the head of the result list
    return head;
}
  
/* Function to print Nodes in a given linked list */
static void printList(Node Node)
{
    while (Node != null) {
        System.out.print(Node.key+ " ");
        Node = Node.next;
    }
}
  
/* Utility function to create a new node with
   given key */
static Node newNode(int key)
{
    Node temp = new Node();
    temp.key = key;
    temp.next = null;
    return temp;
}
  
/* Driver program to test above functions*/
public static void main(String[] args)
{
    /* Start with the empty list */
    Node res = null;
  
    /* Let us create two sorted linked lists to test
       the above functions. Created lists shall be
         a: 5.10.15.40
         b: 2.3.20  */
    Node a = newNode(5);
    a.next = newNode(10);
    a.next.next = newNode(15);
    a.next.next.next = newNode(40);
  
    Node b = newNode(2);
    b.next = newNode(3);
    b.next.next = newNode(20);
  
    System.out.print("List A before merge: \n");
    printList(a);
  
    System.out.print("\nList B before merge: \n");
    printList(b);
  
    /* merge 2 sorted Linked Lists */
    res = sortedMerge(a, b);
  
    System.out.print("\nMerged Linked List is: \n");
    printList(res);
}
}
  
// This code is contributed by umadevi9616

C#

/*Given two sorted linked lists consisting of N and M nodes
respectively. The task is to merge both of the list
(in-place) and return head of the merged list.*/
  
using System;
using System.Collections.Generic;
  
public class GFG{
  
/* Link list Node */
public class Node {
    public int key;
    public Node next;
};
  
// Function to reverse a given Linked List using Recursion
static Node reverseList(Node head)
{
  
    if (head.next == null)
        return head;
  
    Node rest = reverseList(head.next);
    head.next.next = head;
    head.next = null;
  
    return rest;
}
  
// Given two non-empty linked lists 'a' and 'b'
static Node sortedMerge(Node a, Node b)
{
    
    // Reverse Linked List 'a'
    a = reverseList(a);
  
    // Reverse Linked List 'b'
    b = reverseList(b);
  
    // Initialize head of resultant list
    Node head = null;
  
    Node temp;
  
    // Traverse both lists while both of them
    // have nodes.
    while (a != null && b != null) {
  
        // If a's current value is greater than or equal to
        // b's current value.
        if (a.key >= b.key) {
  
            // Store next of current Node in first list
            temp = a.next;
            
            // Add 'a' at the front of resultant list
            a.next = head;
            
            // Make 'a' - head of the result list
            head = a;
            
            // Move ahead in first list
            a = temp;
        }
        
        // If b's value is greater. Below steps are similar
        // to above (Only 'a' is replaced with 'b')
        else {
  
            temp = b.next;
            b.next = head;
            head = b;
            b = temp;
        }
    }
  
    // If second list reached end, but first list has
    // nodes. Add remaining nodes of first list at the
    // beginning of result list
    while (a != null) {
  
        temp = a.next;
        a.next = head;
        head = a;
        a = temp;
    }
  
    // If first list reached end, but second list has
    // nodes. Add remaining nodes of second list at the
    // beginning of result list
    while (b != null) {
  
        temp = b.next;
        b.next = head;
        head = b;
        b = temp;
    }
  
    // Return the head of the result list
    return head;
}
  
/* Function to print Nodes in a given linked list */
static void printList(Node Node)
{
    while (Node != null) {
        Console.Write(Node.key+ " ");
        Node = Node.next;
    }
}
  
/* Utility function to create a new node with
   given key */
static Node newNode(int key)
{
    Node temp = new Node();
    temp.key = key;
    temp.next = null;
    return temp;
}
  
/* Driver program to test above functions*/
public static void Main(String[] args)
{
    /* Start with the empty list */
    Node res = null;
  
    /* Let us create two sorted linked lists to test
       the above functions. Created lists shall be
         a: 5.10.15.40
         b: 2.3.20  */
    Node a = newNode(5);
    a.next = newNode(10);
    a.next.next = newNode(15);
    a.next.next.next = newNode(40);
  
    Node b = newNode(2);
    b.next = newNode(3);
    b.next.next = newNode(20);
  
    Console.Write("List A before merge: \n");
    printList(a);
  
    Console.Write("\nList B before merge: \n");
    printList(b);
  
    /* merge 2 sorted Linked Lists */
    res = sortedMerge(a, b);
  
    Console.Write("\nMerged Linked List is: \n");
    printList(res);
}
}
  
// This code is contributed by umadevi9616 

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

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