[LeetCode]Remove Linked List Elements

给定头结点和删除的节点，让我们删除指定的节点。做法很简单，一直monitor下一个节点是不是我们要删除的节点即可。注意头结点可能被删除所以head会变化，我们用helper节点来帮我们keep track of新的head节点。O(N)时间，常数空间。代码如下：

	/**
	* 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) {
	ListNode* helper = new ListNode(-1);
	helper->next = head;
	auto curr = helper;
	while(curr->next)
	{
	while(curr->next && curr->next->val != val)
	curr = curr->next;
	if(!curr->next)break;
	auto tmp = curr->next;
	curr->next = tmp->next;
	tmp->next = nullptr;
	}
	return helper->next;
	}
	};

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