203.移除链表元素

方法：定义一个节点指向头节点head，避免头结点单独操作

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