leetcode Remove Linked List Elements

题目连接

https://leetcode.com/problems/remove-linked-list-elements/  

 Remove Linked List Elements

Description

Remove all elements from a linked list of integers that have value val.

Example 
Given: 1 –> 2 –> 6 –> 3 –> 4 –> 5 –> 6, val = 6 
Return: 1 –> 2 –> 3 –> 4 –> 5

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
	ListNode* removeElements(ListNode* head, int val) {
		if (!head) return NULL;
		ListNode *p = head, *x = NULL;
		if (p->val == val) {
			while (p->next && p->val == val) {
				x = p;
				p = x->next;
				delete x;
			}
			head = p;
		}
		while (p && p->next) {
			while (p->next && p->next->val == val) {
				x = p->next;
				p->next = x->next;
				delete x;
			}
			p = p->next;
		}
		return (!head->next && head->val == val) ? NULL : head;
	}
};