21. Merge Two Sorted Lists

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { val = x; } * } */public class Solution {    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {        if(l1==null)            return l2;        if(l2==null)            return l1;        ListNode head;            if(l1.val<l2.val){            head=l1;            l1=l1.next;        }            else{            head=l2;            l2=l2.next;        }        ListNode temp=head;        while(l1!=null&&l2!=null){            if(l1.val<l2.val){                head.next=l1;                l1=l1.next;            }            else{                head.next=l2;                l2=l2.next;            }            head=head.next;        }        if(l1==null)            head.next=l2;        else            head.next=l1;        return temp;        }}