leecode 21. 合并兩個有序連結清單

package com.test.leecode.link;

/**
 * Created by zhanghaipeng on 2019/8/5.
 * Definition for singly-linked list.
 * public class ListNode {
 * int val;
 * ListNode next;
 * ListNode(int x) { val = x; }
 * }
 *
 * 将兩個有序連結清單合并為一個新的有序連結清單并傳回。新連結清單是通過拼接給定的兩個連結清單的所有節點組成的。 
 * 示例：
 * 輸入：1->2->4, 1->3->4
 * 輸出：1->1->2->3->4->4
 *
 * 來源：力扣（LeetCode）
 * 連結：https://leetcode-cn.com/problems/merge-two-sorted-lists
 * 著作權歸領扣網絡所有。商業轉載請聯系官方授權，非商業轉載請注明出處。
 */
class ListNode {
    int val;
    ListNode next;

    ListNode(int x) {
        val = x;
    }
}

/**
 * @author zhanghaipeng
 */
public class CombineTwoLink {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode combine = new ListNode (-1);
        ListNode cur = combine;
        ListNode cur1 = l1;
        ListNode cur2 = l2;
        ListNode temp = null;

        while(cur1 != null || cur2 != null ) {
            if(cur1 == null){
                cur.next = cur2;
                break;
            }
            if(cur2 == null){
                cur.next = cur1;
                break;
            }
            if (cur1.val <= cur2.val) {
                temp = cur1.next;
                cur.next = cur1;
                cur1.next = null;
                cur1 = temp;
                cur = cur.next;
            } else {
                temp = cur2.next;
                cur.next = cur2;
                cur2.next = null;
                cur2 = temp;
                cur = cur.next;
            }
        }

        return combine.next;

    }

    public static void main(String[] args){
        ListNode l1 = new ListNode (1);
        l1.next = new ListNode (2);
        l1.next.next = new ListNode(4);
        l1.next.next.next = new ListNode(5);
        ListNode l2 = new ListNode (1);
        l2.next = new ListNode (3);
        l2.next.next = new ListNode(4);
        new CombineTwoLink ().mergeTwoLists (l1,l2);

    }
}