Given a linked list, swap every two adjacent nodes and return its head.
For example,
Given
Given
1->2->3->4
, you should return the list as 2->1->4->3
.
Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.
Solution:
# Definition for singly-linked list. # class ListNode: # def __init__(self, x): # self.val = x # self.next = None class Solution: # @param a ListNode # @return a ListNode def swapPairs(self, head): dummy = ListNode(0) dummy.next = head previous = dummy while previous.next != None and previous.next.next: node1 = previous.next node2 = previous.next.next previous.next = node2 node1.next = node2.next node2.next = node1 previous = node1 return dummy.next
No comments :
Post a Comment