题解 | #合并两个排序的链表#在while循环中完成所有

/*
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;
        }
        //先找到头部小的那个链表的节点
        ListNode smallNode = list1;
        if(list1.val > list2.val){
            smallNode = list2;
            list2 = list2.next;
        } else {
            list1 = list1.next;
        }

        ListNode head = smallNode;
        while(list1 != null || list2 != null){
            if(list1 == null){
                head.next = list2;
                break;
            }
            if(list2 == null){
                head.next = list1;
                break;
            }

            if(list1.val > list2.val){
                head.next = list2;
                head = head.next;
                list2 = list2.next;
            } else {
                head.next = list1;
                head = head.next;
                list1 = list1.next;
            }
        }

        return smallNode;
    }
}