剑指offer --合并链表

题目：输入两个单调递增的链表，输出两个链表合成后的链表，当然我们需要合成后的链表满足单调不减规则。

解法://递归解法

public class MixLink {

/*
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 list3 = null;

if(list1.val<list2.val){
list3 = list1;
list3.next = Merge(list1.next,list2);
}else if(list1.val>=list2.val){
list3 = list2;
list3.next = Merge(list1,list2.next);
}
return list3;
}
}

解法： 非递归

       while(list1!=null&&list2!=null){

              

             if(list1.val<list2.val){

                 if(list3==null){

                      list3 = list1;

                 }else{

                     list3.next = list1;

                     list3 = list3.next; 

                 }

                 list1 = list1.next;

             }else if(list1.val>list2.val){

                 if(list3 == null){

                      list3 = list2;

                 }else{

                     list3.next = list2;

                     list3 = list3.next;

                 }

                 list2 = list2.next;

             }

              

         }

         if(list1==null){

             list3.next= list2;

         }

         if(list2 == null){

             list3.next = list1;

         }

         return list3;