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