两个有序链表（相邻元素可能相同）找出他们交集，并把结果放到另一链表中

     两个有序链表（相邻元素可能相同），找出他们的交集，并把结果放到另一链表中，代码如下：

typedef struct Node* pNode; 
struct Node
{
    int val;
    struct Node *next;
};

pNode merge(pNode head1, pNode head2)
{
    pNode head = NULL;
    pNode p1 = head1;
    pNode p2 = head2;
    pNode p3 = NULL;
    pNode p4 = NULL;

    
    if (NULL == p1 || NULL == p2)
    {
        return NULL;
    }
    /*先找出相交的第一个元素，并作为存储交集链表的头结点*/
    while (p1 && p2)
    {
        if (p1->val == p2->val)
        {
            head = (pNode)malloc(sizeof(struct Node));
            head->val = p1->val;
            head->next = NULL;
            p1 = p1->next;
            p2 = p2->next;
            break;
        }
        else if (p1->val > p2->val)
        {
            while (p2->next != NULL && p2->val == p2->next->val)
            {
                p2 = p2->next;
            }
                p2 = p2->next;
        }        
        else
        {
            while (p1->next != NULL && p1->val == p1->next->val)
            {
                p1 = p1->next;
            }
            p1 = p1->next;
        }
    }

    p3 = p4 = head;

    while (p1 && p2)
    {
        if (p1->val == p2->val && p1->val != p3->val && p2->val != p3->val)
        {
            p4 = (pNode)malloc(sizeof(struct Node));
            p4->next = NULL;
            p4->val = p1->val;
            p3->next = p4;
            p3 = p4;
            p1 = p1->next;
            p2 = p2->next;
        }
        else if (p1->val > p2->val)
        {
            while (p2->next != NULL && p2->val == p2->next->val)
            {
                p2 = p2->next;
            }
            p2 = p2->next;
        }        
        else
        {
            while (p1->next != NULL && p1->val == p1->next->val)
            {
                p1 = p1->next;
            }
            p1 = p1->next;
        }
    }

    return head;
}