将两个已排序的链表归并成一个链表（C++面试题）

题目：

将两个已经排好序的链表组合成一个排序的链表。

/*归并排序的思想时间：2015年4月8日 19:59:02*/#include <iostream>#include <cstdlib>using namespace std;typedef struct Node//模拟节点{int data;struct Node * next;}NODE,* PNODE;class List{private:PNODE pHead;int len;//链表长度public:List(int _len=0);//初始化链表List(List & blist); //拷贝构造函数~List();void create()const;//随机创建一个链表void traverse1()const;//遍历void bubble_sort();//冒泡排序PNODE Merge(List & blist)const;//归并排序int show(){return len;}//返回长度};void traverse2(PNODE pHead);int main(){int len1,len2;cout<<"请输入一个大于0的数作为第一个链表的长度: ";cin>>len1;cout<<"请输入一个大于0的数作为第二个链表的长度: ";cin>>len2;List A(len1); //长度为len1的链表A.create();//创建A对象链表cout<<"链表A有"<<A.show()<<"个元素"<<",未排序时："<<endl;A.traverse1();cout<<"链表A排序后："<<endl;A.bubble_sort(); //排序A.traverse1();cout<<endl<<endl;List B(len2); //长度为len1的链表B.create();//创建B对象链表cout<<"链表B有"<<B.show()<<"个元素"<<",未排序时："<<endl;B.traverse1();cout<<"链表B排序后："<<endl;B.bubble_sort();//排序B.traverse1();cout<<endl<<endl;cout<<"归并后的链表为："<<endl;PNODE p =A.Merge(B);traverse2(p);cout<<endl<<endl;return 0;}List::List(int _len )//默认链表长度为0{pHead = new NODE;pHead->next = NULL;len = _len;}List::List(List & blist)  //拷贝构造函数{pHead = new NODE;PNODE pTail = pHead;pTail->next = NULL;len = blist.len;for(int i=0; i<len; i++){PNODE pNew = new NODE;pNew->data = blist.pHead->data;pTail->next = pNew;pNew->next = NULL;pTail = pNew;blist.pHead = blist.pHead->next;}}List::~List()//删除链表{NODE * temp = NULL;while(pHead != NULL){temp = pHead->next;delete pHead;pHead = temp;}}void List::create()const//创建长度为len的链表{if(len <= 0)return;int i;PNODE pTail = new NODE;pTail->next = NULL;pTail = pHead;for(i=0; i<len; i++){PNODE pNew = new NODE;pNew->data = rand()%1000; //1000以内的随机非负数pTail->next = pNew;pNew->next = NULL;pTail = pNew;}return;}void List::traverse1()const//遍历{PNODE temp = pHead->next;while(temp != NULL){cout<<temp->data<<" ";temp = temp->next;}cout<<endl;return;}void List::bubble_sort(){if(len <= 1) //长度小于等于1，则不用排序return;int temp;PNODE pTemp = pHead->next;PNODE pNew =pTemp;for(int i=0; i<len-1; i++){for(int j=0; j<len-i-1; j++ ){if( pNew->next && pNew->data > pNew->next->data ){temp = pNew->data;pNew->data = pNew->next->data;pNew->next->data = temp;}pNew = pNew->next;}pNew = pTemp;}return ;}PNODE List::Merge(List & blist) const//归并{int m=0, n=0;//m计数本对象，n计数形参对象PNODE m_temp = pHead->next;PNODE n_temp = blist.pHead->next;PNODE p = new NODE;PNODE pTail = p;pTail->next = NULL;while(m<len && n<blist.len)  //当有一个链表比较完了，另外一个链表只要接上去就OK{if(m_temp->data < n_temp->data){PNODE pNew = new NODE;pNew->data = m_temp->data;pTail->next = pNew;pNew->next = NULL;pTail = pNew;m_temp = m_temp->next;m++;}else if(m_temp->data > n_temp->data){PNODE pNew = new NODE;pNew->data = n_temp->data;pTail->next = pNew;pNew->next = NULL;pTail = pNew;n_temp = n_temp->next;n++;}}//看哪个链表还有没比较完的元素if( m<len ) {pTail->next = m_temp;}else if(n<blist.len){pTail->next = n_temp;}return p;}void traverse2(PNODE pHead) //这个不是类里的遍历函数{PNODE temp = pHead->next;while(temp != NULL){cout<<temp->data<<" ";temp = temp->next;}cout<<endl;return;}