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;
        }
        ListNode curr = pHead1;
        ListNode res = pHead2;
        while (curr != null) {
            ListNode next = curr.next;

            ListNode curr2 = res;
            ListNode prev = null;
            while (curr2 != null) {
                ListNode next2 =  curr2.next;
                if (curr.val <= curr2.val) {
                    curr.next = curr2;
                    if (prev != null) {
                        prev.next = curr;
                    }
                    if (prev == null) {
                        res = curr;
                    }
                    break;
                }
                if (next2 == null) {
                    curr2.next = curr;
                    curr.next = null;
                    break;
                }
                prev = curr2;
                curr2 = next2;
            }
            curr = next;
        }
        return res;
    }
}