Merge pull request vJechsmayr#212 from bislara/0024_swap_nodes

added swap notes in pair solution

Author: vJechsmayr

LeetCode/0024_ Swap_Nodes_in_Pairs.py

@@ -0,0 +1,27 @@
+'''
+Problem:-
+
+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:
+- Given 1->2->3->4, you should return the list as 2->1->4->3.
+
+'''
+
+# Definition for singly-linked list.
+# class ListNode:
+# def __init__(self, val=0, next=None):
+# self.val = val
+# self.next = next
+class Solution:
+ def swapPairs(self, head: ListNode) -> ListNode:
+ pre, pre.next = self, head
+ while pre.next and pre.next.next:
+ a = pre.next
+ b = a.next
+ pre.next, b.next, a.next = b, a, b.next
+ pre = a
+ return self.next
+
+