说明：思路中写的是代码，表达基本意思
一、删除链表中所有与val相等的元素
定义两个结点：prev和cur
遍历整个链表：
相等：prve.next=cur.next
cur=cur.next
prev=prev.next
不相等：cur=cur.next

二、合并两个有序链表
定义两个结点result（合成的新链表的头结点） last(result的最后一个结点)
如果cur1.val<=cur2.val
last.next=cur1
cur1=cur1.next
否则，同理，更新cur2

```class Node { int val; Node next = null; public Node(int val) { this.val = val; }}public class Solution { Node removeAll(Node head, int val) { Node prev = null; Node cur = head; while (cur != null) { if (cur.val == val) { if (cur == head) { head = cur.next; } else { prev.next = cur.next; } } else { prev = cur; } cur = cur.next; } return head; } Node merge(Node head1, Node head2) { if (head1 == null) { return head2; } if (head2 == null) { return head1; } Node result = null; Node last = null; Node cur1 = head1; Node cur2 = head2; while (cur1 != null && cur2 != null) { if (cur1.val <= cur2.val) { if (result == null) { result = cur1; } else { last.next = cur1; } last = cur1; cur1 = cur1.next; } else { if (result == null) { result = cur2; } else { last.next = cur2; } last = cur2; cur2 = cur2.next; } } if (cur1 != null) { last.next = cur1; } else { last.next = cur2; } return result; } public static Node createList() { Node n1 = new Node(6); Node n3 = new Node(2); Node n4 = new Node(6); Node n6 = new Node(4); Node n8 = new Node(6); n1.next = n3; n3.next = n4; n4.next = n6; n6.next = n8; return n1; } public static Node createList1() { Node n1 = new Node(1); Node n2 = new Node(2); n1.next = n2; return n1; } public static Node createList2() { Node n1 = new Node(1); Node n2 = new Node(3); Node n3 = new Node(5); Node n4 = new Node(7); n1.next = n2; n2.next = n3; n3.next = n4; return n1; } public static void main(String[] args) { Node head = createList(); Node result = new Solution().removeAll(head, 6); for (Node cur = result; cur != null; cur = cur.next) { System.out.println(cur.val); } System.out.println("====================="); Node head1 = createList1(); Node head2 = createList2(); Node merged = new Solution().merge(head1, head2);//类中的函数返回值是Node类型，用merge接收 for (Node cur = merged; cur != null; cur = cur.next) {//merge相当于head，代表整个链表 System.out.println(cur.val); } }}