题解 | #合并两个排序的链表#

class Solution {
public:
    ListNode* Merge(ListNode* pHead1, ListNode* pHead2) 
    {
        if(pHead1 == NULL && pHead2 == NULL){
            return pHead1;
        }else if(pHead1 == NULL && pHead2 != NULL){
            return pHead2;
        }else if(pHead1 != NULL && pHead2 == NULL){
            return pHead1;
        }
        ListNode* newhead;
        if(pHead1->val <= pHead2->val){
            newhead = new ListNode(pHead1->val);
            pHead1 = pHead1->next;
        }else{
            newhead = new ListNode(pHead2->val);
            pHead2 = pHead2->next;
        }
        ListNode* last = newhead;
        while(pHead1 != NULL && pHead2 != NULL)
        {
            if(pHead1->val <= pHead2->val)
            {
                last->next = pHead1;
                pHead1 = pHead1->next;
                last = last->next;
            }else{
                last->next = pHead2;
                pHead2 = pHead2->next;
                last = last->next;
            }
        }
        if(pHead1!=NULL)
        {
            last->next = pHead1;
        }else if(pHead2 != NULL)
        {
            last->next = pHead2;
        }
        return newhead;
    }
};