【JAVA、C++】LeetCode 021 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.

解题思路：

新建一个ListNode进行存储即可，JAVA实现如下：

	static public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
		ListNode listnode=new ListNode(0);
		ListNode index=listnode;
		while(l1!=null&&l2!=null){
			if(l1.val>l2.val){
				ListNode temp=l1;
				l1=l2;
				l2=temp;
			}
			index.next=new ListNode(l1.val);
			index=index.next;
			l1=l1.next;
		}
		if(l1==null)
			index.next=l2;
		else 
			index.next=l1;
		return listnode.next;
	}

C++:

 1 class Solution {
 2  public:
 3      ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
 4          if (l1 == NULL)
 5              return l2;
 6          else if (l2 == NULL)
 7              return l1;
 8          ListNode* start;
 9          if (l1->val < l2->val) {
10              start = l1;
11              l1 = l1->next;
12          }
13          else {
14              start = l2;
15              l2 = l2->next;
16          }
17          ListNode* cur = start;
18          while (l1 != NULL&&l2 != NULL) {
19              if (l1->val < l2->val) {
20                  cur->next = l1;
21                  cur = cur->next;
22                  l1 = l1->next;
23              }
24              else {
25                  cur->next = l2;
26                  cur = cur->next;
27                  l2 = l2->next;
28              }
29          }
30          if (l1 == NULL)
31              cur->next = l2;
32          else
33              cur->next = l1;
34          return start;
35      }
36  };