将两个链表整合到一个

在这里插入代码片/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
        ListNode* head=new ListNode(1);
        ListNode* ret=head;
        while(l1!=NULL&&l2!=NULL)
        {
            if(l1->val<l2->val)
            {
                head->next=l1;
                l1=l1->next;
            }
            else
            {
                head->next=l2;
                l2=l2->next;
            }
            head=head->next;
        }
        head->next=l1==NULL?l2:l1;
        return ret->next;
    }
};