Related Articles

# XOR Linked List – Pairwise swap elements of a given linked list

• Last Updated : 18 Jan, 2021

Given a XOR linked list, the task is to pairwise swap the elements of the given XOR linked list .

Examples:

Input: 4 <-> 7 <-> 9 <-> 7
Output: 7 <-> 4 <-> 7 <-> 9
Explanation:
First pair of nodes are swapped to formed the sequence {4, 7} and second pair of nodes are swapped to form the sequence {9, 7}.

Input: 1 <-> 2 <-> 3
Output: 2 <-> 1 <-> 3

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: The problem can be solved using the concept of Pairwise swap elements of a given linked list. The idea is to traverse the given xor-linked list and select two adjacent pair of nodes and swap them. Follow the steps below to solve the problem:

Below is the implementation of the above approach:

## C

 `// C program to implement ` `// the above approach ` `#include ` `#include ` `#include ` ` `  `// Structure of a node ` `// in XOR linked list ` `struct` `Node { ` ` `  `    ``// Stores data value ` `    ``// of a node ` `    ``int` `data; ` ` `  `    ``// Stores XOR of previous ` `    ``// pointer and next pointer ` `    ``struct` `Node* nxp; ` `}; ` ` `  `void` `pairwiseswap(``struct` `Node**); ` `void` `swap(``int``*, ``int``*); ` ` `  `// Function to find the XOR of two nodes ` `struct` `Node* XOR(``struct` `Node* a, ``struct` `Node* b) ` `{ ` `    ``return` `(``struct` `Node*)((``uintptr_t``)(a) ` `                          ``^ (``uintptr_t``)(b)); ` `} ` ` `  `// Function to insert a node with ` `// given value at given position ` `struct` `Node* insert(``struct` `Node** head, ` `                    ``int` `value) ` `{ ` ` `  `    ``// If XOR linked list is empty ` `    ``if` `(*head == NULL) { ` ` `  `        ``// Initialize a new Node ` `        ``struct` `Node* node ` `            ``= (``struct` `Node*)``malloc``( ` `                ``sizeof``(``struct` `Node)); ` ` `  `        ``// Stores data value in ` `        ``// the node ` `        ``node->data = value; ` ` `  `        ``// Stores XOR of previous ` `        ``// and next pointer ` `        ``node->nxp = XOR(NULL, NULL); ` ` `  `        ``// Update pointer of head node ` `        ``*head = node; ` `    ``} ` ` `  `    ``// If the XOR linked list ` `    ``// is not empty ` `    ``else` `{ ` ` `  `        ``// Stores the address ` `        ``// of current node ` `        ``struct` `Node* curr = *head; ` ` `  `        ``// Stores the address ` `        ``// of previous node ` `        ``struct` `Node* prev = NULL; ` ` `  `        ``// Initialize a new Node ` `        ``struct` `Node* node ` `            ``= (``struct` `Node*)``malloc``( ` `                ``sizeof``(``struct` `Node)); ` ` `  `        ``// Update curr node address ` `        ``curr->nxp = XOR(node, ` `                        ``XOR(NULL, curr->nxp)); ` ` `  `        ``// Update new node address ` `        ``node->nxp = XOR(NULL, curr); ` ` `  `        ``// Update head ` `        ``*head = node; ` ` `  `        ``// Update data value of ` `        ``// current node ` `        ``node->data = value; ` `    ``} ` `    ``return` `*head; ` `} ` ` `  `// Function to pairwise swap the nodes ` `// of the XOR-linked list ` `void` `pairwiseswap(``struct` `Node** head) ` `{ ` ` `  `    ``// Stores pointer of current node ` `    ``struct` `Node* curr = (*head); ` ` `  `    ``// Stores pointer of previous node ` `    ``struct` `Node* prev = NULL; ` ` `  `    ``// Stores pointer of next node ` `    ``struct` `Node* next = NULL; ` ` `  `    ``// Traverse the XOR-linked list ` `    ``while` `(curr != NULL ` `           ``&& curr->nxp != XOR(prev, NULL)) { ` ` `  `        ``next = XOR(prev, curr->nxp); ` `        ``prev = curr; ` `        ``curr = next; ` ` `  `        ``// Swap the elements ` `        ``swap(&prev->data, &curr->data); ` ` `  `        ``// Update next ` `        ``next = XOR(prev, curr->nxp); ` ` `  `        ``// Update prev ` `        ``prev = curr; ` ` `  `        ``// Update curr ` `        ``curr = next; ` `    ``} ` `} ` ` `  `// Function to swap two numbers ` `void` `swap(``int``* a, ``int``* b) ` `{ ` `    ``int` `temp; ` `    ``temp = *a; ` `    ``*a = *b; ` `    ``*b = temp; ` `} ` ` `  `// Function to print elements of ` `// the XOR Linked List ` `void` `printList(``struct` `Node** head) ` `{ ` `    ``// Stores XOR pointer ` `    ``// in current node ` `    ``struct` `Node* curr = *head; ` ` `  `    ``// Stores XOR pointer of ` `    ``// in previous Node ` `    ``struct` `Node* prev = NULL; ` ` `  `    ``// Stores XOR pointer of ` `    ``// in next node ` `    ``struct` `Node* next; ` ` `  `    ``// Traverse XOR linked list ` `    ``while` `(curr != NULL) { ` ` `  `        ``// Print current node ` `        ``printf``(``"%d "``, curr->data); ` ` `  `        ``// Forward traversal ` `        ``next = XOR(prev, curr->nxp); ` ` `  `        ``// Update prev ` `        ``prev = curr; ` ` `  `        ``// Update curr ` `        ``curr = next; ` `    ``} ` `} ` ` `  `// Driver Code ` `int` `main() ` `{ ` ` `  `    ``/* Create following XOR Linked List ` `    ``head -->7 –> 6 –>8 –> 11 –> 3 –> 1 –> 2 –> 0*/` `    ``struct` `Node* head = NULL; ` ` `  `    ``insert(&head, 0); ` `    ``insert(&head, 2); ` `    ``insert(&head, 1); ` `    ``insert(&head, 3); ` `    ``insert(&head, 11); ` `    ``insert(&head, 8); ` `    ``insert(&head, 6); ` `    ``insert(&head, 7); ` ` `  `    ``// Swap the elements pairwise ` `    ``pairwiseswap(&head); ` ` `  `    ``// Print the new list ` `    ``printList(&head); ` ` `  `    ``return` `(0); ` `} `

Output:

```6 7 11 8 1 3 0 2
```

Time Complexity: O(N)
Auxiliary Space: O(N)

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.  To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

In case you wish to attend live classes with experts, please refer DSA Live Classes for Working Professionals and Competitive Programming Live for Students.

My Personal Notes arrow_drop_up
Recommended Articles
Page :