21. Merge Two Sorted Lists

旧城等待， 2022-08-21 04:08 125阅读 0赞

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.

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/**
 * 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 pre=new ListNode(-1);
        ListNode res=pre;
        while(l1!=null||l2!=null){
            if(l1!=null&&l2!=null){
                if(l1.val<l2.val){
                    pre.next=l1;
                    l1=l1.next;
                }
                else{
                    pre.next=l2;
                    l2=l2.next;
                }
            }
            else if(l1!=null){
                pre.next=l1;
                l1=l1.next;
            }
            else if(l2!=null){
                pre.next=l2;
                l2=l2.next;
            }
            pre=pre.next;
        }
        return res.next;
    }
}