203. Remove Linked List Elements

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

这道题要注意边界，比如[1], 1. 所以这个题的loop condition最好只用当前nood。

public ListNode RemoveElements(ListNode head, int val) {
        if(head == null) return head;
        var sentinel = new ListNode(0);
        sentinel.next = head;
        var temp = sentinel;
        while(head != null)
        {
            if(head.val == val)  temp.next = head.next;
            else  temp = temp.next;
            head = head.next;
        }
        return sentinel.next;
    }