Leetcode86. Partition List分隔链表（双指针）

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

class Solution {

public:

    ListNode* partition(ListNode* head, int x) {

        ListNode* less_head = new ListNode(0);

        ListNode* more_head = new ListNode(0);

        ListNode* p = less_head;

        ListNode* q = more_head;

        while(head)

        {

            if(head ->val < x)

            {

                less_head ->next = head;

                less_head = less_head ->next;

            }

            else

            {

                more_head ->next = head;

                more_head = more_head ->next;

            }

            head = head ->next;

        }

        more_head ->next = NULL;

        less_head ->next = q ->next;

        return p ->next;

    }

};