链表问题（二）——有序链表合并

struct Node
{
int data;
Node *next;
};
//方法一：递归实现
Node *Merge（Node *head1,Node *head2）
{
if(head1 == NULL)
return head2;
if(head2 == NULL)
return head1;
Node *head=NULL;
if(head1->data < head2->data)
{
head = head1;
head->next = Merge(head1->next, head2);
}
else
{
head = head2;
head->next = Merge(head1,head2->next);
}
return head;
}

//方法二：循环实现
Node * Merge(Node * head1,Node *head2)
{
if(head1 == NULL)
return head2;
if(head2 == NULL)
return head1;
Node *head = NULL;
Node *p1 = NULL;
Node *p2 = NULL;
if(head1->data <= head2->data)
{
head=head1;
p1=head1->next;
p2=head2;
}
else
{
head = head2;
p1=head1;
p2 = head2->next;
}
Node *pcurr=head;
while(p1 != NULL && p2 != NULL)
{
if(p1->data < p2->data)
{
pcurr->next = p1;
pcurr = p1;
p1 = p1->next;
}
else
{
pcurr->next = p2;
pcurr = p2;
p2 = p2->next;
}
}
while(p1 != NULL)
{
pcurr->next = p1;
pcurr = p1;
p1 = p1->next;
}
while(p2 != NULL)
{
pcurr->next = p2;
pcurr = p2;
p2 = p2->next;
}
return head;
}