合并两个排序的链表

/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
	public ListNode Merge(ListNode list1, ListNode list2) {
		if (list1 == null) {
			return list2;
		}
		if (list2 == null) {
			return list1;
		}
		ListNode head = null;
		if (list1.val <= list2.val) {
			head = list1;
			head.next = Merge(list1.next, list2);
		} else {
			head = list2;
			head.next = Merge(list1, list2.next);
		}
		return head;
	}
}