C++实现合并两个排序的链表

struct ListNode {  int val;  struct ListNode *next;  ListNode(int x) :  val(x), next(NULL) {  }};

class Solution {public:  ListNode* Merge(ListNode* pHead1, ListNode* pHead2)  {    ListNode* newList = NULL; //新链表头    ListNode* newListRear = NULL; //新链表尾    // 先处理某个链表为空的情形    if (pHead1 == NULL){      return pHead2;    }    if (pHead2 == NULL){      return pHead1;    }    // 把数值小的结点放入新链表，生成头节点    if (pHead1->val <= pHead2->val){      newList = pHead1;      newListRear = pHead1;      pHead1 = pHead1->next;    }else{      newList = pHead2 ;      newListRear = pHead2;      pHead2 = pHead2->next;    }    // 两表均不空的情形下，遍历     while (pHead1 != NULL && pHead2 != NULL) {      if (pHead1->val <= pHead2->val) {        newListRear->next =pHead1;        newListRear = pHead1;        pHead1 = pHead1->next;      }else{        newListRear->next =pHead2;        newListRear = pHead2;        pHead2 = pHead2->next;      }    }    //某一表为空时，把另一表接入新表表尾     if (pHead1 == NULL) {      newListRear->next = pHead2;    }    if (pHead2 == NULL) {      newListRear->next = pHead1;    }        return newList;  }};

class Solution {public:  ListNode* Merge(ListNode* pHead1, ListNode* pHead2)  {    if (pHead1 == NULL){      return pHead2;    }    if (pHead2 == NULL){      return pHead1;    }        if (pHead1->val <= pHead2->val){ // pHead1为合并后的头节点      pHead1->next = Merge(pHead1->next, pHead2);      return pHead1;    }else{ // pHead2 为合并后的头节点      pHead2->next = Merge(pHead1, pHead2->next);      return pHead2;    }  }};