leetcode-21Merge Two Sorted Lists

带头结点

import  java.util.* ;

class ListNode {
	  int val;
	  ListNode next;
	  ListNode(int x) { val = x; }
 }


public class Solution {
	    
	   public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
	          ListNode head = new ListNode(0)  ;
	          ListNode now = head ;
	          while(l1 != null &&  l2 != null){
	        	    if(l1.val <= l2.val){
	        	    	   now.next = new ListNode(l1.val) ;
	        	    	   l1 = l1.next ;
	        	    }
	        	    else{
	        	    	   now.next = new ListNode(l2.val) ; 
	        	    	   l2 = l2.next ;
	        	    }
	        	    now = now.next ;
	          }
	          while(l1 != null){
	        	    now.next = new ListNode(l1.val) ;
   	    	        l1 = l1.next ;
   	    	        now = now.next ;
	          }
	          while(l2 != null){
	        	    now.next = new ListNode(l2.val) ;
 	    	        l2 = l2.next ;
 	    	        now = now.next ;
	          }
	          return  head.next ;
	   }

	    
	   public static void main(String[] args){
		     
	   }
	   
}