合并两个升序链表，要点在于：边界条件判断，即链表可能为空。
剩下的
/*
1: 边界条件判断
2: 头结点的值
3:
*/
Node * mergeOrderedLinkedList(Node *head1, Node *head2)
{
//边界条件判断
if(null == head1) return head2;
if(null == head2) return head1;
Node *head = null, *p1 = null, *p2 = null;
//获取头结点
if(head1->value < head2->value)
{
head = head1;
p1 = head1->next;
p2 = head2;
}
else
{
head = head2;
p2 = head2->next;
p1 = head1;
}
//依次合并
Node *p3 = head;
while(null != p1 && null != p2)
{
if(p1->value < p2->value)
{
p3->next = p1;
p3 = p1;
p1 = p1->next;
}
else
{
p3->next = p2;
p3 = p2;
p2 = p2->next;
}
}
if(null == p1)
{
p3->next = p2;
}
else{
p3->next = p1;
}
return head;
}
（2）递归实现。
按照上面的算法实现，思路很清晰简单，但是代码太长。可以知道每次循环的动作都是相似的，用递归应该可以实现。如下
[cpp]
Node * mergeOrderedLinkedListRecursive(Node *head1, Node *head2)
{
//边界条件判断
if(null == head1) return head2;
if(null == head2) return head1;
Node *head = null; www.2cto.com
if(head1->value < head2->value)
{
head = head1;
head->next = mergeOrderedLinkedListRecursive(head1->next, head2);
}
else
{
head = head2;
head->next = mergeOrderedLinkedListRecursive(head1, head2->next);
}
return head;
}