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) {
        // write code here
        ListNode hair = new ListNode(0);
        ListNode pointer = hair;
        while (pHead1 != null || pHead2 != null) {
            if (pHead1 == null) {
                pointer.next = pHead2;
                return hair.next; 
            } else if (pHead2 == null) {
                pointer.next = pHead1;
                return hair.next;
            } else if (pHead1.val < pHead2.val) {
                pointer.next = pHead1;
                pHead1 = pHead1.next; 
            } else {
                pointer.next = pHead2;
                pHead2 = pHead2.next;
            }
            pointer = pointer.next;
        }
        return hair.next;
    }
}