Add solution 328 [Java]

Author: yanglbme

README.md

@@ -11,12 +11,11 @@
 </p>
 
 ## Introduction
-Complete solutions to Leetcode problems, updated daily.
+Complete [solutions](https://github.com/doocs/leetcode/tree/master/solution) to Leetcode problems, [updated daily](https://github.com/doocs/leetcode/projects/1).
 
 ## Solution List
 
-<detail>
-<summary><b>Easy</b></summary>
+### Easy
 
 | # | Title | Tags |
 |---|---|---|
@@ -41,11 +40,8 @@ Complete solutions to Leetcode problems, updated daily.
 | 703 | [Kth Largest Element in a Stream](https://github.com/doocs/leetcode/tree/master/solution/703.Kth%20Largest%20Element%20in%20a%20Stream) | `Heap` |
 | 876 | [Middle of the Linked List](https://github.com/doocs/leetcode/tree/master/solution/876.Middle%20of%20the%20Linked%20List) | `Linked List` |
 
-</detail>
 
-
-<detail>
-<summary><b>Medium</b></summary>
+### Medium
 
 | # | Title | Tags |
 |---|---|---|
@@ -71,11 +67,10 @@ Complete solutions to Leetcode problems, updated daily.
 | 144 | [Binary Tree Preorder Traversal](https://github.com/doocs/leetcode/tree/master/solution/144.Binary%20Tree%20Preorder%20Traversal) | `Stack`, `Tree` |
 | 150 | [Evaluate Reverse Polish Notation](https://github.com/doocs/leetcode/tree/master/solution/150.Evaluate%20Reverse%20Polish%20Notation) | `Stack` |
 | 153 | [Find Minimum in Rotated Sorted Array](https://github.com/doocs/leetcode/tree/master/solution/153.Find%20Minimum%20in%20Rotated%20Sorted%20Array) | `Array`, `Binary Search` |
+| 328 | [Odd Even Linked List](https://github.com/doocs/leetcode/tree/master/solution/328.Odd%20Even%20Linked%20List) | `Linked List` |
 
-</detail>
 
-<detail>
-<summary><b>Hard</b></summary>
+### Hard
 
 | # | Title | Tags |
 |---|---|---|
@@ -85,10 +80,9 @@ Complete solutions to Leetcode problems, updated daily.
 | 145 | [Binary Tree Postorder Traversal](https://github.com/doocs/leetcode/tree/master/solution/145.Binary%20Tree%20Postorder%20Traversal) | `Stack`, `Tree` |
 | 295 | [Find Median from Data Stream](https://github.com/doocs/leetcode/tree/master/solution/295.Find%20Median%20from%20Data%20Stream) | `Heap`, `Design` |
 
-</detail>
 
 ## Contributions
-I'm looking for long-term contributors/partners to this repo! Send me PRs if you're interested! See the following:
+I'm looking for long-term contributors/partners to this repo! Send me [PRs](https://github.com/doocs/leetcode/pulls) if you're interested! See the following:
 - Fork this repository to your own GitHub account and then [clone](https://help.github.com/articles/cloning-a-repository/) it to your local device.
 - Submit a pull request with your changes!
 

solution/328.Odd Even Linked List/README.md

@@ -0,0 +1,66 @@
+## 奇偶链表
+### 题目描述
+
+给定一个单链表，把所有的奇数节点和偶数节点分别排在一起。请注意，这里的奇数节点和偶数节点指的是节点编号的奇偶性，而不是节点的值的奇偶性。
+
+请尝试使用原地算法完成。你的算法的空间复杂度应为 O(1)，时间复杂度应为 O(nodes)，nodes 为节点总数。
+
+**示例 1:**
+```
+输入: 1->2->3->4->5->NULL
+输出: 1->3->5->2->4->NULL
+```
+
+**示例 2:**
+```
+输入: 2->1->3->5->6->4->7->NULL 
+输出: 2->3->6->7->1->5->4->NULL
+```
+
+**说明:**
+
+- 应当保持奇数节点和偶数节点的相对顺序。
+- 链表的第一个节点视为奇数节点，第二个节点视为偶数节点，以此类推。
+
+### 解法
+利用 `pre`, `cur`指针指向链表的第 1、2 个结点，循环：将 `cur` 的下一个结点挂在 `pre` 的后面，`pre` 和 `cur` 指针向右移动。
+
+eg. 
+```
+1->2->3->4->5: `pre`指向 1,`cur`指向 2
+第一次循环后：1->3->2->4->5: `pre`指向 2, `cur`指向 4
+...
+```
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public ListNode oddEvenList(ListNode head) {
+        // 链表结点数小于 3,直接返回
+        if (head == null || head.next == null || head.next.next == null) {
+            return head;
+        }
+        ListNode dummy = new ListNode(-1);
+        dummy.next = head;
+        ListNode pre = head, t = pre.next, cur = t;
+        while (cur != null && cur.next != null) {
+            pre.next = cur.next;
+            cur.next = cur.next.next;
+            pre.next.next = t;
+            pre = pre.next;
+            // cur.next可能为空，所以在下一次循环要判断 cur!= null 是否满足
+            cur = cur.next;
+            t = pre.next;
+        }
+        
+        return dummy.next;
+    }
+}
+```

solution/328.Odd Even Linked List/Solution.java

@@ -0,0 +1,30 @@
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public ListNode oddEvenList(ListNode head) {
+        // 链表结点数小于 3,直接返回
+        if (head == null || head.next == null || head.next.next == null) {
+            return head;
+        }
+        ListNode dummy = new ListNode(-1);
+        dummy.next = head;
+        ListNode pre = head, t = pre.next, cur = t;
+        while (cur != null && cur.next != null) {
+            pre.next = cur.next;
+            cur.next = cur.next.next;
+            pre.next.next = t;
+            pre = pre.next;
+            // cur.next可能为空，所以在下一次循环要判断 cur != null 是否满足
+            cur = cur.next;
+            t = pre.next;
+        }
+        
+        return dummy.next;
+    }
+}