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