JZ25 合并两个排序的链表

描述

输入两个递增的链表，单个链表的长度为n，合并这两个链表并使新链表中的节点仍然是递增排序的。

数据范围： 0 ≤n≤1000，−1000≤节点值≤1000
要求：空间复杂度 O(1)，时间复杂度 O(n)

public ListNode Merge(ListNode head1,ListNode head2){
    ListNode dummy = new ListNode(0);
    ListNode cur = dummy;
    if(head1 == null)
        return head2;
     if(head2 == null)
        return head1;
    while(head1 != null && head2 != null){
        if(head1.val <= head2.val){
            cur.next = head1;
            head1 = head1.next;
        }
        else{
            cur.next = head2;
            head2 = head2.next;
        }
        cur = cur.next;
    }
    cur.next = (head1 == null) ? head2 : head1;
    return dummy.next;

}