LeetCode----Partition List

Partition List

Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.

You should preserve the original relative order of the nodes in each of the two partitions.

For example,

Given 

1->4->3->2->5->2

 and x = 3,

return 

1->2->2->4->3->5

.

分析：

实现链表的分割，类似于快排中的分割。

我的方法非常简单，遍历链表，建立两个链表，s表示小链表，里面的元素值均小于给定元素x；b表示大链表，里面的元素均大于等于给定元素x。

遍历时，对每个节点进行判断，然后放入对应的s或b的链表，最后再将s和b链表进行连接返回。

代码：

class Solution(object):
def partition(self, head, x):
"""
:type head: ListNode
:type x: int
:rtype: ListNode
"""
p = head
ss = s = ListNode(-1) # ss record the start of smaller linkedlist, s record the node in smaller linkedlist
sb = b = ListNode(-1) # sb record the start of bigger linkedlist, b record the node in bigger linkedlist
while p:
if p.val >= x:
b.next = p
p = p.next
b = b.next
b.next = None
else:
s.next = p
p = p.next
s = s.next
s.next = None
s.next = sb.next
return ss.next