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.
给一个链表，和一个整数x， 要求把所有比x小的节点放到前边，把比x大的节点放到后边。
代码：
参考代码
解题思路：弄一个 less链表和greate链表，遍历head链表，对应的大小值分别给less和greater链表，最后把greate链表链接在less 的后边。
