21. Merge Two Sorted Lists

楞做。

public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if(l1 == null || l2 == null) return l1 == null ? l2:l1;
        
        ListNode res = new ListNode(0);
        ListNode temp = res;
        ListNode temp1 = l1;
        ListNode temp2 = l2;
        while(temp1 != null && temp2 != null){
            if(temp1.val < temp2.val){
                temp.next = temp1;
                temp1 = temp1.next;
            }else{
                temp.next = temp2;
                temp2 = temp2.next;
            }
            temp = temp.next;
        }
        
        if(temp1 == null) temp.next = temp2;
        else temp.next = temp1;
        
        return res.next;
    }
}

回头看了眼二刷，发现二刷做的很屌啊。。

public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) 
    {
        if(l1 == null || l2 == null) return l1 == null? l2:l1;
        

            if(l1.val < l2.val)
            {
                l1.next = mergeTwoLists(l1.next,l2);
                return l1;
            }
            else
            {
                l2.next = mergeTwoLists(l1,l2.next);
                return l2;
            }
        
        
    }
}

难道我退步了。。