Swap_Nodes_In_Pairs.py

Given a linked list, swap every two adjacent nodes and return its head.

You may not modify the values in the list-s nodes. Only nodes itself 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 <= 100


# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next



# My Solution
class Solution:
    def swapPairs(self, head: ListNode) -> ListNode:
        
        dummy = ListNode()
        dummy.next = head
        current = dummy
        
        while current.next and current.next.next:
            
            node_1 = current.next
            node_2 = current.next.next
            
            node_1.next = node_2.next
            current.next = node_2
            current.next.next = node_1
            
            current = current.next.next
            
        return dummy.next