forked from keon/algorithms
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathswap_in_pairs.py
More file actions
30 lines (27 loc) · 759 Bytes
/
swap_in_pairs.py
File metadata and controls
30 lines (27 loc) · 759 Bytes
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
"""
Given a linked list, swap every two adjacent nodes
and return its head.
For example,
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.
"""
class Node(object):
def __init__(self, x):
self.val = x
self.next = None
def swap_pairs(head):
if not head:
return head
start = Node(0)
start.next = head
current = start
while current.next and current.next.next:
first = current.next
second = current.next.next
first.next = second.next
current.next = second
current.next.next = first
current = current.next.next
return start.next