牛客-剑指0ffer-合并两个排序的链表

题目描述
输入两个单调递增的链表，输出两个链表合成后的链表，当然我们需要合成后的链表满足单调不减规则。

/*
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 = new ListNode(0);
        ListNode root = head;
        
        while (list1 != null && list2 != null){
            if (list1.val < list2.val){
                head.next = list1;
                list1 = list1.next;
            }else{
                head.next = list2;
                list2 = list2.next;
            }
            head = head.next;
           
        }
         if (list1 != null){
                head.next = list1;
            }
        if (list2 != null){
            head.next = list2;
        }
        return root.next;
    }
}