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;
    }
};