Remove Linked List Elements

https://leetcode.com/problems/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

解题思路：

这两天leetcode上多了不少190+的easy题目，正好解解心头的郁闷，前面留下的骨头都太难啃了。

这题很简单，几个技巧。1. dummy节点。2. 当前节点时刻保留在要判断的前一个，这样才可以remove。

一遍AC，时间复杂度O(n)。

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode removeElements(ListNode head, int val) {
        ListNode dummy = new ListNode(0);
        dummy.next = head;
        ListNode current = dummy;
        while(current.next != null) {
            if(current.next.val == val) {
                current.next = current.next.next;
            } else {
                current = current.next;
            }
        }
        return dummy.next;
    }
}