leetcode 86 分隔链表
z
 2019-07-05 17:35:02  

给定一个链表和一个特定值 x，对链表进行分隔，使得所有小于 x 的节点都在大于或等于 x 的节点之前。

你应当保留两个分区中每个节点的初始相对位置。

示例:

输入: head = 1->4->3->2->5->2, x = 3
输出: 1->2->2->4->3->5

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# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def partition(self, head, x):
        """
        :type head: ListNode
        :type x: int
        :rtype: ListNode
        """
        if not head:
            return head
        
        dump = ListNode(-1)
        dump.next = head
        p = head
        pre = dump
        
        outer = ListNode(-1)
        outerPre = outer
        
        while p:
            if p.val >= x:
                pre.next = p.next
                outerPre.next = p
                p.next = None
                outerPre = outerPre.next
                p = pre.next
            else:
                p = p.next
                pre = pre.next
        pre.next = outer.next
        return dump.next