C++链表归并排序示例

/*
 * description:        链表归并排序示例
 * writeby:            nick
 * date:            2012-10-23 16:35
 *
 */

#include <iostream>
#define maxN 10

using namespace std;

struct node
{
    int item;
    node *next;
    node(int n){item=n; next=0;}
};
typedef node *link;

link merge(link a, link b)    //合并a b 链表
{
    node dummy(0);
    link head=&dummy, c=head;
    while((a!=0) && (b!=0))
    {
        if(a->item < b->item)
        {
            c->next=a; c=a; a=a->next;
        }
        else
        {
            c->next=b; c=b; b=b->next;
        }
    }
    c->next = (a==0)? b : a;
    return head -> next;
}

link mergesort(link c)
{
    if(c==0 || c->next==0) return c;
    link a=c, b=c->next;
    while(b!=0 && b->next!=0)
    {
        a=a->next; b=b->next->next;
    }
    b=a->next; a->next=0;    //把c分成两部分
    return merge(mergesort(c), mergesort(b));
}

int main()
{
    link head1 = new node(2);
    head1->next = new node(4);
    head1->next->next = new node(6);
    head1->next->next->next = new node(3);
    head1->next->next->next->next = new node(5);

    link head = mergesort(head1);

    while(head != 0)
    {
        cout << head->item;
        head = head->next;
    }

    return 0;
}