牛客网-剑指offer-两个链表重新排序

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题目描述
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。

listNode.java

public class ListNode {    int val;    ListNode next=null;    ListNode(int val){        this.val=val;    }}

LinkList.java

public class LinkList {    public ListNode  first;    private int pos=0;    public LinkList(){        this.first=null;    }    public void addFirstNode(int data){        ListNode node=new ListNode(data);        node.next=first;        first=node;    }    public void print(){        ListNode mynode=this.first;        while(mynode!=null){            System.out.print(mynode.val+"   ");            mynode=mynode.next;        }        System.out.println();    }    public ListNode getFirstNode(){        return  this.first;    }}

Solution.java

package mergeTwoList;/** * Created by Administrator on 2017/3/16. */public class Solution {    public ListNode Merge(ListNode list1,ListNode list2) {            ListNode mylist=null;            ListNode fistNode=null;            if(list1==null){                return list2;            }            if(list2==null){                return list1;            }            while((list1!=null)&&(list2!=null)){                if(list1.val<=list2.val){                    if(fistNode==null) {                        mylist=fistNode=new ListNode(list1.val);                        list1=list1.next;                    }else{                    mylist.next=new ListNode(list1.val);                    list1=list1.next;                    mylist=mylist.next;}                }else{                    if(fistNode==null){                        mylist=fistNode=new ListNode(list2.val);                        list2=list2.next;                    }else{                    mylist.next=new ListNode(list2.val);                    list2=list2.next;                    mylist=mylist.next;                    }                }            }            if(list1==null){                mylist.next=list2;            }else{                mylist.next=list1;            }            return fistNode;    }}

test.java

package mergeTwoList;import java.util.LinkedList;/** * Created by Administrator on 2017/3/16. */public class test{    public static void main(String[] args){        Solution myso=new Solution();        LinkList mylist_one=new LinkList();        mylist_one.addFirstNode(8);        mylist_one.addFirstNode(6);        mylist_one.addFirstNode(3);        mylist_one.addFirstNode(1);        LinkList mylist_two=new LinkList();        mylist_two.addFirstNode(13);        mylist_two.addFirstNode(10);        mylist_two.addFirstNode(8);        mylist_two.addFirstNode(5);        mylist_two.addFirstNode(3);        mylist_two.addFirstNode(1);        ListNode mylist_thrid_first=null;        mylist_thrid_first=myso.Merge(mylist_one.getFirstNode(),mylist_two.getFirstNode());        while(mylist_thrid_first!=null){            System.out.print(mylist_thrid_first.val+"    " );            mylist_thrid_first=mylist_thrid_first.next;        }    }}

这一种方法比较好想。
=============华丽的分隔线===============
还有一种递归的方法。

 public ListNode Merge(ListNode list1,ListNode list2){        if(list1==null){            return list2;        }        if(list2==null){            return list1;        }        if(list1.val<=list2.val){            list1.next=Merge(list1.next,list2);            return list1;        }else{            list2.next=Merge(list1,list2.next);            return list2;        }    }

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