链表合并

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。
解题：本题可有循环也可由递归实现，代码给出了递归实现的方式。
代码：
class Solution {
public:
ListNode* Merge(ListNode* pHead1, ListNode* pHead2)
{

if (pHead1 == NULL) return pHead2;if (pHead2 == NULL) return pHead1;ListNode *mergeList = NULL;if (pHead1->val < pHead2->val) {    mergeList = pHead1;    mergeList->next = Merge(pHead1->next, pHead2);}else {    mergeList = pHead2;    mergeList->next = Merge(pHead1, pHead2->next);}return mergeList;

}
};