86. 分隔链表

[yankewei]

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

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/partition-list

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func partition(head *ListNode, x int) *ListNode {
    beforeTmp := &ListNode{}
    afterTmp := &ListNode{}
    before := beforeTmp
    after := afterTmp

    for head != nil {
        if head.Val < x {
            beforeTmp.Next = head
            beforeTmp = beforeTmp.Next 
        } else {
            afterTmp.Next = head
            afterTmp = afterTmp.Next
        }
        head = head.Next
    }
    afterTmp.Next = nil
    beforeTmp.Next = after.Next
    return before.Next
}