In this post, you will know how to solve the Swap Nodes in Pairs Leetcode Solution problem of Leetcode. This Leetcode problem is done in many programming languages like C++, Java, and Python.Swap Nodes in Pairs Leetcode SolutionsOne more thing to add, don’t directly look for the solutions, first try to solve the problems of Leetcode by yourself. If you find any difficulty after trying several times, then you can look for solutions.ProblemGiven a linked list, swap every two adjacent nodes and return its head. You must solve the problem without modifying the values in the list’s nodes (i.e., only nodes themselves may be changed.)Example 1:Input: head = [1,2,3,4] Output: [2,1,4,3] Example 2:Input: head = [] Output: [] Example 3:Input: head = [1] Output: [1] Constraints:The number of nodes in the list is in the range [0, 100].0 <= Node.val <= 100Swap Nodes in Pairs Leetcode Solutions in Pythonclass Solution: def swapPairs(self, head: ListNode) -> ListNode: def getLength(head: ListNode) -> int: length = 0 while head: length += 1 head = head.next return length length = getLength(head) dummy = ListNode(0, head) prev = dummy curr = head for _ in range(length // 2): next = curr.next curr.next = next.next next.next = prev.next prev.next = next prev = curr curr = curr.next return dummy.next Swap Nodes in Pairs Leetcode Solutions in CPPclass Solution { public: ListNode* swapPairs(ListNode* head) { const int length = getLength(head); ListNode dummy(0, head); ListNode* prev = &dummy; ListNode* curr = head; for (int i = 0; i < length / 2; ++i) { ListNode* next = curr->next; curr->next = next->next; next->next = prev->next; prev->next = next; prev = curr; curr = curr->next; } return dummy.next; } private: int getLength(ListNode* head) { int length = 0; for (ListNode* curr = head; curr; curr = curr->next) ++length; return length; } }; Swap Nodes in Pairs Leetcode Solutions in Javaclass Solution { public ListNode swapPairs(ListNode head) { final int length = getLength(head); ListNode dummy = new ListNode(0, head); ListNode prev = dummy; ListNode curr = head; for (int i = 0; i < length / 2; ++i) { ListNode next = curr.next; curr.next = next.next; next.next = curr; prev.next = next; prev = curr; curr = curr.next; } return dummy.next; } private int getLength(ListNode head) { int length = 0; for (ListNode curr = head; curr != null; curr = curr.next) ++length; return length; } } Note: This problem Swap Nodes in Pairs is generated by Leetcode but the solution is provided by BrokenProgrammers. This tutorial is only for Educational and Learning purposes.Next: Reverse Nodes in k-Group Leetcode Solution Post navigationNext Permutation Leetcode Solution Reverse Nodes in k-Group Leetcode Solution