题解 | #合并两个排序的链表#

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param pHead1 ListNode类 
     * @param pHead2 ListNode类 
     * @return ListNode类
     */
    public ListNode Merge (ListNode pHead1, ListNode pHead2) {
        if(pHead1 == null) return pHead2;
        if(pHead2 == null) return pHead1;

        ArrayList<ListNode> arr = new ArrayList<>();
        while(pHead1!= null || pHead2 != null) {
            if(pHead1 == null) {
                while(pHead2 != null) {
                    arr.add(pHead2);
                    pHead2 = pHead2.next;
                }
                break;
            }
            if(pHead2 == null) {
                while(pHead1 != null) {
                    arr.add(pHead1);
                    pHead1 = pHead1.next;
                }
                break;
            }
            if( pHead1.val <= pHead2.val) {
                arr.add(pHead1);
                System.out.println(pHead1.val);
                pHead1 = pHead1.next;
            } else {
                arr.add(pHead2);
                System.out.println(pHead2.val);
                pHead2 = pHead2.next;
            }
        }
        System.out.println("size:" + arr.size());
        if(arr.isEmpty()) return null;

        ListNode a = arr.get(0);
        ListNode cur = a;
        for(int i = 1; i < arr.size(); i++) {
            cur.next = arr.get(i);
            cur = cur.next; 
        }
        return a;
    }

}