86. Partition List【M】【48】【leetcode题解】

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.

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class Solution(object):    def partition(self, head, x):        h = head                new_h = ListNode(0)        new_head = new_h                previous = ListNode(0)        prv = previous        #其中，pre是比x大的，h是比x小的        prv.next = h#~!!!!!!!这句话非常重要！！因为最开始如果没有这句的话，就没有进行初始化，pre就只是一个空的头        while h:            if h.val < x:                new_h.next = h                new_h = h                                prv.next = h.next                h = h.next                else:                prv = h                h = h.next         new_h.next = previous.next        return new_head.next