CS-Notes/notes/25. 合并两个排序的链表.md
2020-11-17 00:32:18 +08:00

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Java

# 25. 合并两个排序的链表
[NowCoder](https://www.nowcoder.com/practice/d8b6b4358f774294a89de2a6ac4d9337?tpId=13&tqId=11169&tPage=1&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking&from=cyc_github)
## 题目描述
<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/c094d2bc-ec75-444b-af77-d369dfb6b3b4.png" width="400"/> </div><br>
## 解题思路
### 递归
```java
public ListNode Merge(ListNode list1, ListNode list2) {
if (list1 == null)
return list2;
if (list2 == null)
return list1;
if (list1.val <= list2.val) {
list1.next = Merge(list1.next, list2);
return list1;
} else {
list2.next = Merge(list1, list2.next);
return list2;
}
}
```
### 迭代
```java
public ListNode Merge(ListNode list1, ListNode list2) {
ListNode head = new ListNode(-1);
ListNode cur = head;
while (list1 != null && list2 != null) {
if (list1.val <= list2.val) {
cur.next = list1;
list1 = list1.next;
} else {
cur.next = list2;
list2 = list2.next;
}
cur = cur.next;
}
if (list1 != null)
cur.next = list1;
if (list2 != null)
cur.next = list2;
return head.next;
}
```