合并两个有序单链表

题目原型：

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

直接贴代码吧：

public ListNode mergeTwoLists(ListNode l1, ListNode l2) {        if(l1==null&&l2==null)        return null;        else if(l1==null)        return l2;        else if(l2==null)        return l1;        else        {        ListNode p,q,head,t;        p = l1;        q = l2;        head = p.val<=q.val?p:q;        while(p!=null&&q!=null)        {        if(p.val<=q.val)        {        t = p.next;        if(t!=null)        if(q.val<t.val)        {        p.next = q;        p = t;        }        else        {        p = t;        }        else        {        p.next = q;        break;        }                }        else        {        t = q.next;        if(t!=null)        if(p.val<=t.val)        {        q.next = p;        q = t;        }        else        {        q = t;        }        else        {        q.next = p;        break;        }        }        }        return head;        }