leetcode 21. 合并两个有序链表

直接合并即可

这道题是简单题，直接合并即可
/**

• 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 mergeTwoLists(ListNode list1, ListNode list2) {
  // head是空的，返回的是head.next
  ListNode head = new ListNode();
  ListNode p1 = list1;
  ListNode p2 = list2;
  ListNode newList = head;
  while (p1 != null && p2 != null) {
  int value = 0;
  if (p1.val <= p2.val) {
  value = p1.val;
  p1 = p1.next;
  } else {
  value = p2.val;
  p2 = p2.next;
  }
  ListNode Node = new ListNode(value);
  newList.next = Node;
  newList = newList.next;
  }
  while (p1 != null) {
  ListNode Node = new ListNode(p1.val);
  p1 = p1.next;
  newList.next = Node;
  newList = newList.next;
  }
  while (p2 != null) {
  ListNode Node = new ListNode(p2.val);
  p2 = p2.next;
  newList.next = Node;
  newList = newList.next;
  }
  return head.next;
  }
  }