题目：

题目分析：

题目分析转载

代码实现：

package BMP4;

import java.util.List;

class ListNode {
    int val;
    ListNode next = null;
    public ListNode(int val) {
        this.val = val;
    }
}
public class BM4 {
    /**
     * 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 dummy = new ListNode(-1);
        ListNode pre = dummy;
        while (pHead1 != null && pHead2 != null){
            if (pHead1.val < pHead2.val) {
                pre.next = pHead1;
                pHead1 = pHead1.next;
            }else {
                pre.next = pHead2;
                pHead2 = pHead2.next;
            }
            pre = pre.next;
        }
        if (pHead1 != null) {
            pre.next = pHead1;
        }
        if (pHead2 != null) {
            pre.next = pHead2;
        }
        return dummy.next;
    }
}