C++版 - 剑指offer 面试题17: 合并两个排序的链表 题解

/*
struct ListNode {
	int val;
	struct ListNode *next;
	ListNode(int x) :
			val(x), next(NULL) {
	}
};*/
class Solution {
public:
    ListNode* Merge(ListNode* pHead1, ListNode* pHead2)
    {
     	ListNode *res, *p;
        if(pHead1==NULL) return pHead2;
        if(pHead2==NULL) return pHead1;
        
        if(pHead1->val < pHead2->val)
        {
         	res=pHead1;
            pHead1=pHead1->next;
        }
        else {
            res=pHead2;
            pHead2=pHead2->next;
        }
        
        p=res;
        while(pHead1 != NULL && pHead2 != NULL)
        {
            if(pHead1->val < pHead2->val)
            {
                p->next=pHead1;
                pHead1=pHead1->next;
            }
            else {
                 p->next=pHead2;
                 pHead2=pHead2->next;
            }
            
            p=p->next;
        }
            
        if(pHead1 != NULL)   p->next=pHead1;
        else if(pHead2 != NULL)  p->next=pHead2;
        
        return res;
    }
};