Leetcode题解 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.

合并链表。

/**
 * 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&&l2!=null){
            return l2;
        }else if(l1!=null&&l2==null){
            return l1;
        }else if(l1==null&&l2==null){
            return null;
        }
        ListNode temp;
        if(l1.val<l2.val){
            temp=l1;
            l1=l1.next;
        }else{
            temp=l2;
            l2=l2.next;
        }
        ListNode result=temp;

        while(l1!=null&&l2!=null){
            if(l1.val<l2.val){
                temp.next=l1;
                temp=temp.next;
                l1=l1.next;
            }else{
                temp.next=l2;
                temp=temp.next;
                l2=l2.next;
            }
        }
        if(l1==null&&l2!=null){
            temp.next=l2;
        }else if(l1!=null&&l2==null){
            temp.next=l1;
        }else{
            temp.next=null;
        }
            return result;
    }
}