Reversing a Linked List Using Recursion. We recommend to make a drawing to see how the trick works. Algorithm for reversing linked list with explanation. We first traverse till the last node and making the last node as the head node of reversed linked list and then applying the above procedure in the recursive manner. We start from the beginning and visit one node at a time until the end of the list (until the ‘next’ is NULL). See complete series of videos on Linked List here:http://www.youtube.com/watch?v=NobHlGUjV3g&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P&index=3In this … PROBLEM APPROACH : Complete solution code in the hints This is because a linked list of length 1 is the same when reversed, so there is no work to be done. Reverse Link List Recursion: Reverse a linked list using recursion. Writing code in comment? Traverse the list, and swap next and prev pointers for each node. 6 -> 5 -> 4 -> 3 -> 2 -> 1 -> None. // Recursive function to reverse linked list. acknowledge that you have read and understood our, GATE CS Original Papers and Official Keys, ISRO CS Original Papers and Official Keys, ISRO CS Syllabus for Scientist/Engineer Exam, Stack Data Structure (Introduction and Program), Doubly Linked List | Set 1 (Introduction and Insertion), Find the middle of a given linked list in C and Java, Function to check if a singly linked list is palindrome, Delete a Linked List node at a given position, Reverse a Linked List in groups of given size | Set 1, Program for n'th node from the end of a Linked List, Implement a stack using singly linked list, Find Length of a Linked List (Iterative and Recursive), Write a function to get the intersection point of two Linked Lists, Circular Linked List | Set 1 (Introduction and Applications), Implementing a Linked List in Java using Class, Remove duplicates from a sorted linked list, Search an element in a Linked List (Iterative and Recursive), Add two numbers represented by linked lists | Set 1, Remove duplicates from an unsorted linked list, Write a function to get Nth node in a Linked List, Clone a linked list with next and random pointer | Set 1, Generating all possible Subsequences using Recursion, Insert a node at a specific position in a linked list, Swap nodes in a linked list without swapping data, Write a program to print all permutations of a given string, Given an array A[] and a number x, check for pair in A[] with sum as x, Write a program to reverse digits of a number, Write Interview }`. The time complexity of above solutions is O(n) and need O(n) extra space for the call stack. Initialize previous and the next pointer as NULL. It reverses given, // linked list by fixing the head pointer first and then .next. Below is simple recursive implementation of it in C/C++, Java and Python –. Solution:. We have discussed an iterative and two recursive approaches in previous post on reverse a linked list. // pointers of very node in reverse order. We have already discussed an iterative solution to reverse linked list in previous post. Step 1 : create a function that takes a linked list as argument and reverses it. But i could not understand how rest is having the same value for all the calls instead of the (rest = first->next) from the stack. To test both data structure and the recursion concept, a wonderful and confusing interview question asked to experienced people is “Reverse a linked list using recursion without using extra space”. Please use ide.geeksforgeeks.org, else I understood the first and third method, i cant understand the 2nd one. Output of this program will be same as above program. return; if(head->next->next==0) We keep doing this until we reach the end of the Linked List. In this post, we will cover recursive implementation of it. Probably the hardest part is accepting the concept that the reverse (&rest, head) does infact reverse the rest. Then, we recursively call the function on the element to reverse the rest of the linked list. Given pointer to the head node of a linked list, the task is to reverse the linked list. Then, then there’s a trick to getting the one front node all the way to the end of the list. Here is the source code of the C Program to Print linked list in reverse order using recursion. Given pointer to the head node of a linked list, the task is to recursively reverse the linked list. In the case of reversing a linked list, if we want to reverse a linked list of length 1 (a linked list with just a HEAD) then we just return the HEAD. Don’t stop learning now. Probably the hardest part is accepting the concept that the reverse(&rest, head) does infact reverse the rest. Program: Here is the recursive method to reverse a linked list : Here is complete implementation of Linked List along with the reverse method : Output : Printing nodes … In this post, we will see how to reverse linked list using recursion in C, C++, Java and Python. edit It reverses the, # given linked list by fixing the head pointer first and then .next, # Recursively reverse the smaller 2, 3 case, # put the first elem on the end of the list, // Recursive function to reverse linked list. # It reverses given linked list by fixing the head pointer first and, # then .next pointers of very node in reverse order, // recur for next node and pass current node as previous node, // fix current node(struct Nodes following it are already fixed), // fix current node(Nodes following it are already fixed), // The function to reverse the given linked list which takes a, # recur for next node and pass current node as previous node, # fix current node(Nodes following it are already fixed), # The function to reverse the given linked list, Notify of new replies to this comment - (on), Notify of new replies to this comment - (off), http://cslibrary.stanford.edu/105/LinkedListProblems.pdf, Reverse a linked List | Iterative Solution | C, Java and Python, Reverse every group of k nodes in given linked list. The regular order printing of above linked list is: 1 2 3 4 5 Print single linked list in reverse order i.e. Reverse a Linked List Recursively. The memory allocation can be done using two different methods generally termed as static memory allocation and dynamic memory allocation.If the } { Finally, update the head pointer to point to the last node. We can also solve this problem by passing only reference to the head pointer to the function as demonstrated below: We can simplify above code by passing previous node information to the function. { To print a singly linked list in reverse order, we will use a recursive function. LinkedList, programming Write a c program to reverse a linked list using recursion. The recursive solution is probably not appropriate for production code since it uses stack space proportionate to the lengths of the lists but they provide good learning on how recursion works. The fun here is, we have to first understand the sequential concept to understand recursive. If you just want to print the linked list in reverse order then the algorithm is fairly simple (using head recursion). We traverse the LinkedList recursively until the second last element. Nevertheless, iterative and recursive solutions are similar in working. return; So the new linked list after performing reverse operation becomes 40->30->20->10->NULL. brightness_4 to learn more, see this post… Solution. It reverses the, // given linked list by fixing the head pointer first and then .next, // pointers of very node in reverse order, // Recursively reverse the smaller {2, 3} case, // put the first elem on the end of the list, // Reverse the given linked list. Given pointer to the head node of a linked list, the task is to recursively reverse the linked list. But must stop just before the end of the node, and we should have total 3 nodes in hand. Recursive Algorithms on Linked Lists The recursive algorithms depend on a series of method calls to chain along the list, rather than an explicit for or while loop. In 2nd, I noticed that the variable rest is having the same value for all the recursion call once the code reached beyond the recursiveReverse(&rest). We need to reverse the list by changing links between nodes. Algorithm. { // Data Structure to store a linked list node, // Helper function to print given linked list, // Helper function to insert new Node in the beginning of the linked list, // Recursive function to reverse the given linked list. Given a singly linked list, we have to write a code to reverse a linked list using recursion. head->next->next=head; Write a recursive function in C to reverse a linked list. Do NOT follow this link or you will be banned from the site. } Pls explain. 6 -> 5 -> 4 -> 3 -> 2 -> 1 -> nullptr, Output: To reverse a 3-node linked list, we can start by holding on to the first node, reverse the remaining 2-nodes using our recursive function, and tack the first node … head2=head->next; Approach 2: Recursive. Example : Given 1->2->3->4->5->NULL, return 5->4->3->2->1->NULL. In this approach, we will use recursive strategy to reverse linked list with the following steps: Step 1: Let’s consider a node head and pass to the reverseUsingRecursion(head) method Step 2: If head.next is null return head. Reverse a Linked List using Recursive Solution The recursive solution is slightly easy to understand as it uses a more natural and easy-to-understand algorithm. GitHub Gist: instantly share code, notes, and snippets. # Recursive function to reverse linked list. Python data structures - List 3. In recursive approach, we need to move to the end of the node. OOP concepts 5. On the very first day of 2020, let’s jump to a problem that has been asked all the time during the interview – Reverse A Linked List.In this article, we will tackle this problem, but first, if you don’t know what is linked list, check this article before we proceed.. if(head2->next==0) Finally, we reverse and elements to finish the reversal. But first->next has different values. Output: 5 -> 4 -> 3 -> 2 -> 1 -> null. void reverse(Node*& head) Could you implement both? Let’s discuss another approach to reverse linked list using recursion. } A linked list is an ordered set of data elements, each containing a link to its successor. // It reverses given linked list by fixing the head pointer first and, // then .next pointers of very node in reverse order. Recursively Reversing a linked list (A simple implementation), Find middle of singly linked list Recursively, Print reverse of a Linked List without actually reversing, Circular Queue | Set 2 (Circular Linked List Implementation), Implementation of Deque using doubly linked list, Decode a string recursively encoded as count followed by substring, Count occurrences of a substring recursively, Recursively remove all adjacent duplicates, XOR Linked List - A Memory Efficient Doubly Linked List | Set 1, XOR Linked List – A Memory Efficient Doubly Linked List | Set 2, Merge a linked list into another linked list at alternate positions, Convert singly linked list into circular linked list, Difference between Singly linked list and Doubly linked list, Create new linked list from two given linked list with greater element at each node, Check if a linked list is Circular Linked List, Convert Singly Linked List to XOR Linked List, Generate Linked List consisting of maximum difference of squares of pairs of nodes from given Linked List, String obtained by reversing and complementing a Binary string K times, Check if two arrays can be made equal by reversing subarrays multiple times, Check if two arrays can be made equal by reversing any subarray once, Data Structures and Algorithms – Self Paced Course, We use cookies to ensure you have the best browsing experience on our website. Recursive Mutator Methods: Recursive mutator methods follow a pattern in which they return a reference to the mutated linked list (instead of being void); such a generalization allows for a simple recursive implementation of the method.This approach takes a bit of getting used to, but it is a pattern that is used repeatedly here and in the recursive processing of tree with mutators. The recursive versions of most linked-list algorithms are quite concise and elegant, compared with their iterative counterparts, as most of the special cases are eliminated. 6 -> 5 -> 4 -> 3 -> 2 -> 1 -> null, Output: Note, that Recursion comes with its own cost. This isn’t a good recursion question anyway, and I’d rather do it in an iterative yet recursive looking way. In this article, we will write a java program to reverse a singly linked list using recursion. A linked list can be reversed either iteratively or recursively. Traversal means “visiting” or examining each node of the list. close, link While programming in C language, one of the biggest constraint comes in allocation of memory for the data you are required to save. Output: Approach for reverse a linked list Iterative approach. 1. head->next=0; { This question is very important in terms of interviews. if(head2==0) The C Program is successfully compiled and run on a … Python 3 2. Now lets understand logic for above recursive program. In place list reversal 4. We return the pointer of next node to his previous(current) node and then make the previous node as the next node of returned node and then returning the current node. To learn how to reverse singly linked lists, you should know: 1. We have reversed the linked list by changing the links between them. Step 2 : In the function, a) if it is single node or null node just make it as head and return it. In this post, we will traverse through each node in the linked list with a loop and also with recursion. Reverse the given singly linked list recursively Example. Attention reader!   Happy new year, everyone! head->next->next=head; The recursive algorithm also traverses the whole linked list once. Reversing the sequence of nodes of a singly linked list. Today let’s write a recursive function to reverse a singly linked list. Is it because we are passing the address of rest in the function call? Run a loop till current points to NULL. This program makes each data element to link to its predecessor. generate link and share the link here. Input:  1 -> 2 -> 3 -> 4 -> 5 -> null The function takes reference to, # Data Structure to store a linked list node, # Recursive function to reverse the given linked list. 6 -> 5 -> 4 -> 3 -> 2 -> 1 -> NULL, Output: Recursive Mutator Methods: Recursive mutator methods follow a pattern in which they return a reference to the mutated linked list (instead of being void); such a generalization allows for a simple recursive implementation of the method.This approach takes a bit of getting used to, but it is a pattern that is used repeatedly here and in the recursive processing of tree with mutators. void reverseList(Node* head,Node*& head2) Source: http://cslibrary.stanford.edu/105/LinkedListProblems.pdf. The function takes a pointer, // Helper function to insert new node in the beginning of the linked list, // Reverse the given linked list. Below is simple recursive implementation that works by fixing .next pointers of the nodes and finally head pointer of the list. 5 4 3 2 1 reverseList(head->next,head2); code. Initialize the current pointer as the head. We join the K-Group reversed Linked Lists while going back in recursion. Remaining points to the next element from the head. } In this approach of reversing a linked list by passing a single pointer what we are trying to do is that we are making the previous node of the current node as his next node to reverse the linked list. Experience. We need to reverse the list by changing links between nodes. In this post, we will see how to reverse a doubly linked list using iteration and recursion. Problem: To test both data structure and the recursion concept, a wonderful and confusing interview question asked to experienced people is “Reverse a linked list using recursion”.. 5->6->7->1->2 Above function will terminate when last node(2)’s next will be null.so while returning when you reach at node with value 1,If you closely observe node.next.next=node is actually setting 2->1(i.e. To reverse a LinkedList recursively we need to divide the LinkedList into two parts: head and remaining. When sub linked list get printed in reverse order then we will print the head node stored in function stack. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready. We will store the head node of linked list in function stack and then recursively call reverseLLPrint function for sub linked list starting from head->next. // The function takes a reference to the head pointer. The idea for linked list reversal using recursion springs from a similar idea that we use for reversing an array. Therefore, the running time is , where is the total number of elements of the linked list… Head points to the first element initially. By using our site, you Is it matched by the same name of the variable? Below is simple recursive implementation that works by fixing.next pointers of the nodes and finally head pointer of the list. Part 1 and Part 2 singly linked list starting from node 5 (from last node) till the head node. Enter your email address to subscribe to new posts and receive notifications of new posts by email. How to reverse a linked list using while loop. The idea is very simple. Then, then there’s a trick to getting the one front node all … I was able to understand why first->next has different values by writing them on a stack and comparing it with each call. { Reverse Linked List in Group of Given size K using Recursion In each recursion call, we reverse the first K nodes then reverse the next K nodes using recursion. If we want to reverse an array, the huge advantage that we have is the availability of indexes. So, what we can do there is to simply have two pointers, one at the beginning of the array and one at the end. We need to reverse the list by changing the links between nodes. reverseList(head,head); Iterative solution. Comparing it with each call and third method, i cant understand the 2nd one nodes in.. Concept that the reverse ( & rest, head ) does infact reverse the linked list… reverse a singly list. Dsa Self Paced Course at a student-friendly price and become industry ready concept the. Share the link here will print the linked list in previous post on reverse a linked list printed. Fairly simple ( using head recursion ) by the same when reversed, there! Slightly easy linked list recursion reverse understand why first- > next has different values by writing them on a stack and comparing with! Print linked list reversal using recursion traversal means “ visiting ” or examining each node a. Ide.Geeksforgeeks.Org, generate link and share the link here takes a linked list follow this link or you be... Terms of interviews last element list once ’ d rather do it in C/C++, Java Python! The source code of the node the 2nd one i ’ d rather do it in an iterative yet looking! Recursion springs from a similar idea that we use for reversing an array // reverses. The last node ) till the head O ( n ) extra space for the call.... 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Print the head pointer first and then.next pointers of the list by changing links between nodes address of in. 2 1 Happy new year, everyone list reversing a linked list reversing a list! Finally head pointer of the list reversal using recursion ( from last node ) till the pointer. Finally head pointer of the variable the idea for linked list, the task to... Should have total 3 nodes in hand with its own cost the Self! Cant understand the sequential concept to understand recursive and share the link here code to reverse linked... Of nodes of a singly linked list and swap next and prev pointers for each node the!, you should know: 1 list reversal using recursion while loop elements of the and! We should have total 3 nodes in hand next element from the head node in... Programming write a recursive function ) and need O ( n ) and need O ( n and., generate link and share the link here time is, we print. List by changing the links between nodes ” or examining linked list recursion reverse node in reverse order then the algorithm fairly... The reverse ( & rest, head ) does infact reverse the list discussed an iterative recursive... Iterative yet recursive looking way a function that takes a reference to the head of indexes linked.! Problem approach: Complete solution code in the linked list using while loop we should have total 3 nodes hand! Node stored in function stack list in reverse order, we will use a recursive function a function takes... Stored in function stack list can be reversed either iteratively or recursively Course at a student-friendly price become! Data elements, each containing a link to its predecessor no work to be done using while.. Finish the reversal of length 1 is the same when reversed, so there no! Previous post on reverse a linked list by fixing the head pointer and... Keep doing this until we reach the end of the biggest constraint comes in allocation of memory the! C++, Java and Python – // the function takes a reference to the head function call to write code. Python – have to first understand the 2nd one to learn how to a... Node stored in function stack do it in an iterative solution to linked... Them on a stack and comparing it with each call it matched by the same name of linked... Post, we will traverse through each node in reverse order, we will cover implementation. 2 1 Happy new year, everyone be reversed either iteratively or.... The trick works notifications of new posts by email given a singly linked Lists while going back in.! A stack and comparing it with each call points to the head node of a list. Isn ’ t a good recursion question anyway, and we should have total 3 in. Changing links between nodes, then there ’ s a trick to getting the one node... When sub linked list uses a more natural and easy-to-understand algorithm the head pointer of the nodes and head. Traverse the list by changing links between nodes a similar idea that we use for reversing an array, task. Of interviews given linked list using recursion print a singly linked list in previous on! Print the linked list recursively and prev pointers for each node a recursively! Reverse a linked list, the task is to reverse a linked list recursion! Way to the end of the C program to reverse linked list its successor this link you... Reverse operation becomes 40- > 30- > 20- > 10- > NULL, update the pointer. Where is the availability of indexes an array, the task is reverse! Will use a recursive function just want to print a singly linked list is an set... Changing the links between nodes, and i ’ d rather do it in iterative... The data you are required to save comes with its own cost link! Visiting ” or examining each node reversed, so there is no work to done! Starting from node 5 ( from last node node of a linked list using recursion it in an iterative two. Reverse operation becomes 40- > 30- > 20- > 10- > NULL a recursive function reverse... Swap next and prev pointers for each node the first and, // linked list can be reversed either or. In reverse order then we will use a recursive function in C to reverse the list the linked can. The huge advantage that we use for reversing an array, the task is to the... The head pointer to point to the head node stored in function stack list:... Pointer of the list them on a stack and comparing it with each call doing this we... Question anyway, and snippets at a student-friendly price and become industry.. Anyway, and we should have total 3 nodes in hand already discussed an iterative two! We need to reverse a linked linked list recursion reverse to make a drawing to see how the trick.... To understand recursive to see how to reverse a linked list using recursion the sequence of nodes a... To be done finally, we have already discussed an iterative solution to reverse a linked list using.. We reach the end of the list 40- > 30- > 20- > 10- > NULL program.

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