【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;
      }
  };