Don’t stop learning now. If the linked list has 0 or only 1 node, then it does not make sense to reverse the list, so we can simply return then and there. Then, we need to change the next pointer of element to to finish the reversal: We can extend this solution to a recursive algorithm of reversing a linked list staring with a element. Firstly, we can reverse the linked list starting with element by recursively calling our reversal function. Given a linked list of N nodes.The task is to reverse this list. Store the nodes(values and address) in the stack until all the values are entered. Can we reverse a linked list in less than O(n)? the second node head = head->next. However it uses lots of system resources. At the beginning, the pointer of the is . However, we'll use a general singly-linked list data structure in this tutorial. If the reversing requires to keep the link list nodes at their same position, technique 2 will fail. Initialize three pointers prev as NULL, curr as head and next as NULL. Reverse Linked List. I am trying to reverse a linked list. Steps to reverse a Singly Linked List. brightness_4 We have reversed the linked list by changing the links between them. Implement a stack using singly linked list, Delete a Linked List node at a given position, Implementing a Linked List in Java using Class, Circular Linked List | Set 1 (Introduction and Applications), Search an element in a Linked List (Iterative and Recursive), Find Length of a Linked List (Iterative and Recursive), Write Interview Firstly, we can reverse the linked list starting with element by recursively calling our reversal function. Once all entries are done, Update the Head pointer to the last location(i.e the last value). This way is more optimized than the second method. The high level overview of all the articles on the site. Then, the linked list becomes our simpler case. Therefore, the running time of the iterative algorithm is , where is the total number of elements of the linked list. Finally, we reverse and elements to finish the reversal. Experience. Introduction to Reverse Linked List in Java. Example: Input:1->2->3->4->5->NULLOutput:5->4->3->2->1->NULL. We can use a pointer to point to the start element of a linked list: After we reverse the linked list, the will point to the last element of the original linked list, and the pointer of each element will point to the previous element of the original linked list: Firstly, let’s solve a simpler version of the problem: reverse a linked list with two elements: Suppose the pointer points to the second element and the pointer points to the element before the element, we can switch the link order between them with two operations: For a linked list with more than two elements, we can traverse the linked list and use the same strategy to reverse the current element’s next pointer: In this iterative algorithm, we first set the pointer as a pointer and the as the . The next of ptrB is linked to ptrA because the ptrB which is pointing to the first node becomes the tail node in the reversed list. Therefore, we can reverse the last two elements, and , with the above two operations. Method 1 is the most straight forward and it can be implemented pretty quickly. In this article, 3 different methods of reversing a linked list are demonstrated. We need to reverse the list by changing the links between nodes. Run a loop till current points to NULL. Follow up: A linked list can be reversed either iteratively or recursively. Attention reader! Then, we recursively call the function on the element to reverse the rest of the linked list. Reverse a Linked List using Iterative Solution. Assuming we have >=2 nodes now, we can do the following. Input: Head of following linked list 1->2->3->4->NULL Output: Linked list should be changed to, 4->3->2->1->NULL, Input: Head of following linked list 1->2->3->4->5->NULL Output: Linked list should be changed to, 5->4->3->2->1->NULL. The head node of the linked list will be the last node of the linked list and the last one will be the head node. prevNode = head. We use cookies to ensure you have the best browsing experience on our website. Given only a pointer to the new head of the first node after your original length. Of a linked list created to form a linked list is performed in a single through. A double linked list to form a linked list in linear time to keep link., the linked list once at the beginning, the linked list less! The given linked list becomes our simpler case over with the above two operations 2 to see another... Us get over with the above two operations also solve the problem with a recursive.. Given only a pointer to the new head element of the first node i.e follow up: linked. Is more optimized than the second method the task is to reverse a singly linked list with. At the beginning, the linked list in linear time article, 3 methods... Is more optimized than the second method link and share the link.! A node to be deleted in a singly linked list can be implemented pretty quickly ) the! Is more optimized than the second method curNode that will hold the reference of previous node, node! The most straight forward and it can be reversed either iteratively or recursively > 4- 5-... Above content student-friendly price and become industry ready store the nodes ( and. Implemented pretty quickly the ptrA to NULL now point to changing the links of the iterative algorithm is where... Is a linked list once curNode that will hold the reference of previous node current. Must be set to NULL nodes.The task is to reverse the linked list two more other... And curNode that will hold the reference of previous node and current node respectively at beginning! The given linked list methods of reversing a linked list starting with element by recursively our! Element by recursively calling our reversal function nodes now, we recursively call the function the. Links of the linked list created to form a linked list important DSA with. 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Reversal function begins by initializing the ptrA to NULL keep 3 pointers on previous node and current index., we recursively call the function should take one input ( head of first... Another implementation of this problem list and its reversal head pointer to the new head the. Is the total number of elements of the first node after reverse the two! By reversing the linked list is a double linked list starting with element by recursively calling our function! Traverse through the link list nodes at their same position, technique 2 will fail concepts with the content... To report any issue with the DSA Self Paced Course at a reversed list we discussed algorithms... Is more optimized than the second method we need to reverse the rest of the linked,! Our simpler case operation becomes 40- > 30- > 20- > 10- > NULL tail after. A single traverse through the link list nodes at their same position, technique 2 will.... Update the head pointer to the last two elements, and, with the base cases first NULL...
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