Java合并两个有序链表

题目：合并两个有序链表，将两个升序链表合并为一个新的 升序 链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。
合并两个有序链表

• 1.分析
• 2.具体步骤
• 3.代码实现

1. 首先定义一个傀儡结点newHead，让中间结点tmp指向它，两个链表头结点headA和headB
2. 当两个表都不为空就进入循环
3. 首先就将表headA.val和headB.val进行比较，谁小谁就放在newHead的后面，然后头结点后移，tmp后移
4. 循环走完，当两个表有一个为空时，谁不为空，tmp.next就等于谁

public static ListNode mergeTwoLists(ListNode headA, ListNode headB) {
        ListNode newHead = new ListNode(-1);
        ListNode tmp = newHead;
        while (headA != null && headB != null) {
            if (headA.val < headB.val) {
                tmp.next = headA;
                headA = headA.next;
                tmp = tmp.next;
            } else {
                tmp.next = headB;
                headB = headB.next;
                tmp = tmp.next;
            }
        }
        if (headA != null) {
            tmp.next = headA;
        }
        if (headB != null) {
            tmp.next = headB;
        }
        return newHead.next;
    }

测试：

public static void main(String[] args) {
        MylinkedList mylinkedList1 = new MylinkedList();
        mylinkedList1.addLast(12);
        mylinkedList1.addLast(23);
        mylinkedList1.addLast(34);
        mylinkedList1.addLast(45);
        mylinkedList1.addLast(56);
        System.out.println(" mylinkedList1:");
        mylinkedList1.display();

        MylinkedList mylinkedList2 = new MylinkedList();
        mylinkedList2.addLast(13);
        mylinkedList2.addLast(24);
        mylinkedList2.addLast(30);
        System.out.println(" mylinkedList2:");
        mylinkedList2.display();

        ListNode ret=mergeTwoLists(mylinkedList1.head,mylinkedList2.head);
        System.out.println("拼接后:");
        mylinkedList1.display2(ret);

    }