Java编程实现递增排序链表的合并

javascript/198396.html">java;">/* public class ListNode {   int val;   ListNode next = null;    ListNode(int val) {     this.val = val;   } }*/ public class Solution {   public ListNode Merge(ListNode list1,ListNode list2) {     if(list1==null)return list2; //判断到某个链表为空就返回另一个链表。如果两个链表都为空呢？没关系，这时候随便返回哪个链表，不也是空的吗?     if(list2==null)return list1;     ListNode list0=null;//定义一个链表作为返回值     if(list1.val<list2.val){//判断此时的值，如果list1比较小，就先把list1赋值给list0，反之亦然       list0=list1;       list0.next=Merge(list1.next, list2);//做递归，求链表的下一跳的值       }       else{       list0=list2;       list0.next=Merge(list1, list2.next);       }  return list0;   } } 

public class Solution {	public ListNode Merge(ListNode list1,ListNode list2) {		if(list1==null) 		      return list2;		if(list2==null) 		      return list1;		ListNode head;		list0= list1.val>list2.val?list2:list1;		list0.next = list1.val>list2.val?Merge(list1,list2.next):Merge(list1.next,list2);		return list0;	}}

/* public class ListNode {   int val;   ListNode next = null;   ListNode(int val) {     this.val = val;   } }*/public class Solution {	public ListNode Merge(ListNode list1,ListNode list2) {		if(list1 == null) 		        return list2;		if(list2 == null ) 		        return list1;		ListNode tmp1 = list1;		ListNode tmp2 = list2;		ListNode head = new ListNode(0);		//这里不能把返回链表赋值为null，因为下一行马上就要把它赋值给另一链表，得让它在内存里有位置才行 		ListNode headptr = head;		while(tmp1 != null && tmp2!=null){			if(tmp1.val <= tmp2.val) 			          {				head.next=tmp1;				head = head.next;				tmp1 = tmp1.next;			} else{				head.next=tmp2;				head = head.next;				tmp2=tmp2.next;			}		}		//其中一个链表已经跑到头之后，继续单链表的合并 		while(tmp1 != null){			head.next = tmp1;			head = head.next;			tmp1= tmp1.next;		}		while(tmp2 != null){			head.next = tmp2;			head = head.next;			tmp2= tmp2.next;		}		head = headptr.next;		return head;	}}