剑指offer【c++】合并两个排序的链表

剑指offer【c++】合并两个排序的链表

题目：输入两个单调递增的链表，输出两个链表合成后的链表，当然我们需要合成后的链表满足单调不减规则。

思路：比较简单，依次迭代

代码：

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