【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++:

class Solution {
 public:
     ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
         if (l1 == NULL)
             return l2;
         else if (l2 == NULL)
             return l1;
         ListNode* start;
         if (l1->val < l2->val) {
             start = l1;
             l1 = l1->next;
         }
         else {
             start = l2;
             l2 = l2->next;
         }
         ListNode* cur = start;
         while (l1 != NULL&&l2 != NULL) {
             if (l1->val < l2->val) {
                 cur->next = l1;
                 cur = cur->next;
                 l1 = l1->next;
             }
             else {
                 cur->next = l2;
                 cur = cur->next;
                 l2 = l2->next;
             }
         }
         if (l1 == NULL)
             cur->next = l2;
         else
             cur->next = l1;
         return start;
     }
 };