合并链表 【微软面试100题 第二十四题】

题目要求：

　　合并链表。已知链表h1和链表h2都是递增链表，要求合并后也是递增链表。

　　参考链接：http://blog.youkuaiyun.com/v_july_v/article/details/6870251

　　原链接代码while(h1 != NULL && h2 != NULL)应该修改为while(h1 != NULL || h2 != NULL)

代码实现：

#include <iostream>

using namespace std;

typedef struct ListNode
{
    struct ListNode *next;
    int data;
}ListNode;

ListNode *Merge(ListNode *h1, ListNode *h2);
void InitList(ListNode **head1,ListNode **head2);
void PrintList(ListNode *h);

int main(void)
{
    ListNode *h1 = NULL,*h2 = NULL;
    ListNode *mergeList = NULL;
    
    InitList(&h1,&h2);
    cout << "h1:";
    PrintList(h1);
    cout << endl << "h2:";
    PrintList(h2);
    cout << endl;
    mergeList = Merge(h1,h2);
    cout << "mergeList:";
    PrintList(mergeList);

    return 0;
}
void PrintList(ListNode *h)
{
    while(h!=NULL)
    {
        cout << h->data << " ";
        h = h->next;
    }
    cout << endl;
}
ListNode *Merge(ListNode *h1, ListNode *h2) 
{
    if(h1 == NULL) return h2;
    if(h2 == NULL) return h1;
    ListNode *head;
    if(h1->data>h2->data) 
    {
        head = h2; 
        h2=h2->next;
    }
    else 
    {
        head = h1;
        h1=h1->next;
    }

    ListNode *current = head;
    while(h1 != NULL || h2 != NULL) 
    {
        if(h1 == NULL || (h2!=NULL && h1->data>h2->data))
        {
            current->next = h2;
            h2=h2->next; 
            current = current->next;
        }
        else
        {
            current->next = h1;
            h1=h1->next; 
            current = current->next;
        }
    }
    current->next = NULL;
    return head;
}
//head1:1-->5-->9-->NULL
//head2:2-->4-->10-->NULL
void InitList(ListNode **head1,ListNode **head2)
{
    ListNode *tmp = new ListNode;
    tmp->data = 1;
    *head1 = tmp;

    tmp = new ListNode;
    tmp->data = 5;
    (*head1)->next = tmp;

    ListNode *tmp1 = new ListNode;
    tmp1->data = 9;
    tmp1->next = NULL;
    tmp->next = tmp1;

    tmp = new ListNode;
    tmp->data = 2;
    *head2 = tmp;

    tmp = new ListNode;
    tmp->data = 4;
    (*head2)->next = tmp;

    tmp1 = new ListNode;
    tmp1->data = 10;
    tmp1->next = NULL;
    tmp->next = tmp1;
}