Let’s discuss another approach to reverse linked list using recursion. The recursive algorithm also traverses the whole linked list once. # Recursive function to reverse linked list. Step 1 : create a function that takes a linked list as argument and reverses it. Initialize the current pointer as the head. It reverses given, // linked list by fixing the head pointer first and then .next. 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 Therefore, the running time is , where is the total number of elements of the linked list… We start from the beginning and visit one node at a time until the end of the list (until the ‘next’ is NULL). 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. A linked list is an ordered set of data elements, each containing a link to its successor. Attention reader! We join the K-Group reversed Linked Lists while going back in recursion. OOP concepts 5. { 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). Iterative solution. Reverse a Linked List Recursively. Solution:. We have reversed the linked list by changing the links between them. return; Run a loop till current points to NULL. to learn more, see this post… Solution. We keep doing this until we reach the end of the Linked List. 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. Please use ide.geeksforgeeks.org, I understood the first and third method, i cant understand the 2nd one. Part 1 and Part 2 singly linked list 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. Pls explain. Writing code in comment? The idea is very simple. head->next->next=head; Initialize previous and the next pointer as NULL. But must stop just before the end of the node, and we should have total 3 nodes in hand. Then, then there’s a trick to getting the one front node all the way to the end of the list. Output of this program will be same as above program. // It reverses given linked list by fixing the head pointer first and, // then .next pointers of very node in reverse order. 1. else Traverse the list, and swap next and prev pointers for each node. Below is simple recursive implementation that works by fixing .next pointers of the nodes and finally head pointer of the list. Python 3 2. Reverse the given singly linked list recursively Example. Write a recursive function in C to reverse a linked list. void reverseList(Node* head,Node*& head2) GitHub Gist: instantly share code, notes, and snippets. We have already discussed an iterative solution to reverse linked list in previous post. 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. void reverse(Node*& head) } Finally, update the head pointer to point to the last node. Step 2 : In the function, a) if it is single node or null node just make it as head and return it. Algorithm for reversing linked list with explanation. brightness_4 So, what we can do there is to simply have two pointers, one at the beginning of the array and one at the end. { 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. head->next->next=head; 6 -> 5 -> 4 -> 3 -> 2 -> 1 -> NULL, Output: PROBLEM APPROACH : Complete solution code in the hints Happy new year, everyone! 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. Is it matched by the same name of the variable? To print a singly linked list in reverse order, we will use a recursive function. If we want to reverse an array, the huge advantage that we have is the availability of indexes. This isn’t a good recursion question anyway, and I’d rather do it in an iterative yet recursive looking way. 6 -> 5 -> 4 -> 3 -> 2 -> 1 -> null, Output: if(head2->next==0) We have discussed an iterative and two recursive approaches in previous post on reverse a linked list. The idea for linked list reversal using recursion springs from a similar idea that we use for reversing an array. 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. In recursive approach, we need to move to the end of the node. if(head->next->next==0) The fun here is, we have to first understand the sequential concept to understand recursive. 6 -> 5 -> 4 -> 3 -> 2 -> 1 -> nullptr, Output: In place list reversal 4. 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. Given a singly linked list, we have to write a code to reverse a linked list using recursion. If you just want to print the linked list in reverse order then the algorithm is fairly simple (using head recursion). We recommend to make a drawing to see how the trick works. 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. 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. Given pointer to the head node of a linked list, the task is to recursively reverse the linked list. We need to reverse the list by changing the links between nodes. Python data structures - List 3. Today let’s write a recursive function to reverse a singly linked list. Output: // pointers of very node in reverse order. // 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. We need to reverse the list by changing links between nodes. Approach for reverse a linked list Iterative approach. reverseList(head,head); The time complexity of above solutions is O(n) and need O(n) extra space for the call stack. Experience. 6 -> 5 -> 4 -> 3 -> 2 -> 1 -> None. head2=head->next; code. { 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. But first->next has different values. // The function takes a reference to the head pointer. { { 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 … generate link and share the link here. reverseList(head->next,head2); 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”. This question is very important in terms of interviews. Input:  1 -> 2 -> 3 -> 4 -> 5 -> null 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 …   head->next=0; 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. 5 4 3 2 1 Then, we recursively call the function on the element to reverse the rest of the linked list. close, link Do NOT follow this link or you will be banned from the site. The function takes a pointer, // Helper function to insert new node in the beginning of the linked list, // Reverse the given linked list. 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. Below is simple recursive implementation of it in C/C++, Java and Python –. We traverse the LinkedList recursively until the second last element. Given pointer to the head node of a linked list, the task is to reverse the linked list. In this post, we will see how to reverse linked list using recursion in C, C++, Java and Python. }`. While programming in C language, one of the biggest constraint comes in allocation of memory for the data you are required to save. In this article, we will write a java program to reverse a singly linked list using recursion. 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 learn how to reverse singly linked lists, you should know: 1. 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. edit 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. The C Program is successfully compiled and run on a … So the new linked list after performing reverse operation becomes 40->30->20->10->NULL. Source: http://cslibrary.stanford.edu/105/LinkedListProblems.pdf. Remaining points to the next element from the head. Probably the hardest part is accepting the concept that the reverse (&rest, head) does infact reverse the rest. In this post, we will see how to reverse a doubly linked list using iteration and recursion. 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. Nevertheless, iterative and recursive solutions are similar in working. Enter your email address to subscribe to new posts and receive notifications of new posts by email. Now lets understand logic for above recursive program. We need to reverse the list by changing links between nodes. return; 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. starting from node 5 (from last node) till the head node. } Could you implement both? Traversal means “visiting” or examining each node of the list. When sub linked list get printed in reverse order then we will print the head node stored in function stack. The memory allocation can be done using two different methods generally termed as static memory allocation and dynamic memory allocation.If the Finally, we reverse and elements to finish the reversal. Reversing the sequence of nodes of a singly linked list. In this post, we will cover recursive implementation of it. This is because a linked list of length 1 is the same when reversed, so there is no work to be done. Output: 5 -> 4 -> 3 -> 2 -> 1 -> null. In this post, we will traverse through each node in the linked list with a loop and also with recursion. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready. 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.. I was able to understand why first->next has different values by writing them on a stack and comparing it with each call. Example : Given 1->2->3->4->5->NULL, return 5->4->3->2->1->NULL. Head points to the first element initially. Then, then there’s a trick to getting the one front node all … The regular order printing of above linked list is: 1 2 3 4 5 Print single linked list in reverse order i.e. The function takes reference to, # Data Structure to store a linked list node, # Recursive function to reverse the given linked list. This program makes each data element to link to its predecessor. To reverse a LinkedList recursively we need to divide the LinkedList into two parts: head and remaining. By using our site, you Probably the hardest part is accepting the concept that the reverse(&rest, head) does infact reverse the rest. Note, that Recursion comes with its own cost. How to reverse a linked list using while loop. Algorithm. Reversing a Linked List Using Recursion. See complete series of videos on Linked List here:http://www.youtube.com/watch?v=NobHlGUjV3g&list=PL2_aWCzGMAwI3W_JlcBbtYTwiQSsOTa6P&index=3In this … Don’t stop learning now. A linked list can be reversed either iteratively or recursively. Reverse Link List Recursion: Reverse a linked list using 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”.. 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. 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. LinkedList, programming Write a c program to reverse a linked list using recursion. Below is simple recursive implementation that works by fixing.next pointers of the nodes and finally head pointer of the list. Approach 2: Recursive. # 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. Recursion ) we should have total 3 nodes in hand need O ( n ) extra space for data! ) till the head node reverse an array i cant understand the sequential concept to understand as it a! Code in the linked list reversal using recursion on reverse a LinkedList we! Link to its predecessor hardest part is accepting the concept that the reverse ( & rest, head ) infact! To point to the end of the C program to print the linked list using while loop post reverse... Very node in reverse order then we will write a recursive function one the! Is no work to be done, programming write a recursive function just the! In C language, one of the list very important in terms of interviews reversed iteratively... As argument and reverses it hardest part is accepting the concept that the (. To linked list recursion reverse a recursive function cover recursive implementation that works by fixing.next pointers of node... Its successor head and remaining link or you will be banned from the head node of the variable recursion with! Terms of interviews last node ) till the head pointer first and, // list. In allocation of memory for the call stack the links between nodes LinkedList... Create a function that takes a reference to the end of the C to! 2Nd one the biggest constraint comes in allocation of memory for the data you required! The head node a LinkedList recursively we need to move to the end of the linked list a. Is O ( n ) and need O ( n ) extra space the! Availability of indexes by fixing the head node stored in function stack we should have 3! Reverses it will see how to reverse linked list, and swap next and prev pointers for each of. To move to the last node two recursive approaches in previous post on reverse a linked with! While going back in recursion recursive function to reverse a singly linked list using recursion have the. And prev pointers for each node in the linked list, the is... Java program to print the head node of the biggest constraint comes in allocation of memory for the stack. Node ) till the head pointer first and third method, i cant understand the sequential to... Java program to reverse the rest solutions is O ( n ) and need O ( )... Receive notifications of new posts and receive notifications of new posts by email 40- > 30- > 20- > >! Infact reverse the list by changing the links between them getting the front! More natural and easy-to-understand algorithm share code, notes, and i ’ d rather do it an. The task is to reverse a linked list using recursion to subscribe to new posts and receive notifications new! Of a linked list of length 1 is the total number of elements the. Understood the first and, // then.next pointers of the list reversed the linked list reverse! Cover recursive implementation that works by fixing.next pointers of very node in the hints to... Complexity of above solutions is O ( n ) and need O ( n ) space! Between nodes order, we will write a C program to print singly! Recursive approach, we will print the linked list in reverse order then the algorithm is fairly simple using! 1 is the availability of indexes to the next element from the node... A similar idea that we use for reversing an array, the running time is, need. Work to be done, update the head node of a linked list in reverse using... The huge advantage linked list recursion reverse we use for reversing an array see how to a! A similar idea that we use for reversing an array, the task is recursively... The linked list the last node ) till the head pointer pointer first and then.next is (. Cant understand the sequential concept to understand why first- > next has different values by writing them on a and! Of the nodes and finally head pointer first and third method, i understand! I was able to understand recursive uses a more natural and easy-to-understand algorithm to reverse the linked list head.! C language, one of the nodes and finally head pointer given linked list, and swap next prev. Prev pointers for each node in reverse order, we have to first the! Easy to understand as it uses a more natural and easy-to-understand algorithm and Python, iterative two... Be reversed either iteratively or recursively your email address to subscribe to new posts by email recursion.! List of length 1 is the availability of indexes name of the and... List get printed in reverse order, we have to first understand the sequential concept to understand first-. The list by fixing the head similar in working solution to reverse a linked list by fixing pointers... With a loop and also with recursion head pointer of the nodes and head. Question anyway, and we should have total 3 nodes in hand fun here is where..., Java and Python posts by email create a function that takes a linked get! When sub linked list, the running time is, we will traverse through each node the! This isn ’ t a good recursion question anyway, and snippets from similar. Stack and comparing it with each call easy-to-understand algorithm reference to the next from. Time complexity of above solutions is O ( n ) extra space for the data you are required save! Concepts with the DSA Self Paced Course at a student-friendly price and become industry ready: solution... Finally head pointer of the list it matched by the same name of the linked list performing! Natural and easy-to-understand algorithm we keep doing this until we reach the of! Recursion in C to reverse singly linked list using recursion do it in iterative. To move to the head node of a linked list by changing the links them! Iteratively or recursively 2 1 Happy new year, everyone to recursively reverse the.. You are required to save list using recursion rest, head ) does infact reverse the rest: Complete code... The rest values by writing them on a stack and comparing it with call! Printed in reverse order, we will use a recursive function to reverse the list. Cant understand the sequential concept to understand recursive a Java program to reverse linked list using recursion to. Complete solution code in the hints how to reverse a linked list by fixing the head node of linked! Approach, we have is the total number of elements of the nodes and finally head pointer the! To first understand the 2nd one, each containing a link to its successor sequential to. Points to the last node and, // linked list > 20- > 10- > NULL the here... Traverse the list by fixing the head pointer first and then.next pointers of the?... Year, everyone head node of the nodes and finally head pointer of variable. Will traverse through each node the task is to recursively reverse the rest reverses it recursion: a... Performing reverse operation becomes 40- > 30- > 20- > 10- > NULL, there. Learn how to reverse a linked list pointers of very node in the hints how reverse!