合并两个链表.leetcode21 《数据结构入门到精通N7》

struct ListNode* mergeTwoLists(struct ListNode* list1, struct ListNode* list2){
    if(list1==NULL)
    return list2;
    if(list2==NULL)
    return list1;
    struct ListNode* cur1=list1;
    struct ListNode* next1=list1;
    struct ListNode* cur2=list2;
    struct ListNode* next2=list2;
    struct ListNode* newhead=NULL;
    struct ListNode* newcur=NULL;
    while(cur1!=NULL && cur2!=NULL)
    {
        if(cur1->val<cur2->val)
        {
            if(newhead==NULL)
            {
                next1=cur1->next;
                newhead=cur1;
                newcur=cur1;
                cur1=next1;
            }
            else
            {
                next1=cur1->next;
                newcur->next=cur1;
                newcur=cur1;
                cur1=next1;
            }
        }
        else
        {
            if(newhead==NULL)
            {
                next2=cur2->next;
                newhead=cur2;
                newcur=cur2;
                cur2=next2;
            }
            else
            {
                next2=cur2->next;
                newcur->next=cur2;
                newcur=cur2;
                cur2=next2;
            }
        }
    }
    //谁不为空就是没插完
    if(cur1!=NULL)
    {
        newcur->next=cur1;
    }
    else
    {
        newcur->next=cur2;
    }
    return newhead;
}