feat(solution): add solution 0138 [Java]

Copy list with random pointer

Author: yanglbme

README.md

@@ -89,6 +89,7 @@ Complete [solutions](https://github.com/doocs/leetcode/tree/master/solution) to
 | 0127 | [Word Ladder](https://github.com/doocs/leetcode/tree/master/solution/0127.Word%20Ladder) | `Breadth-first Search` |
 | 0130 | [Surrounded Regions](https://github.com/doocs/leetcode/tree/master/solution/0130.Surrounded%20Regions) | `Depth-first Search`, `Breadth-first Search`, `Union Find` |
 | 0137 | [Single Number II](https://github.com/doocs/leetcode/tree/master/solution/0137.Single%20Number%20II) | `Bit Manipulation` |
+| 0138 | [Copy List with Random Pointer](https://github.com/doocs/leetcode/tree/master/solution/0138.Copy%20List%20with%20Random%20Pointer) | `Hash Table`, `Linked List` |
 | 0142 | [Linked List Cycle II](https://github.com/doocs/leetcode/tree/master/solution/0142.Linked%20List%20Cycle%20II) | `Linked List`, `Two Pointers` |
 | 0143| [Reorder List](https://github.com/doocs/leetcode/tree/master/solution/0143.Reorder%20List) | `Linked List` |
 | 0144 | [Binary Tree Preorder Traversal](https://github.com/doocs/leetcode/tree/master/solution/0144.Binary%20Tree%20Preorder%20Traversal) | `Stack`, `Tree` |

img/random-list-step1.png

@@ -0,0 +1,67 @@
+## 复制带随机指针的链表
+
+### 题目描述
+
+给定一个链表，每个节点包含一个额外增加的随机指针，该指针可以指向链表中的任何节点或空节点。
+
+![random-list.png](/img/random-list.png)
+
+要求返回这个链表的深度拷贝。 
+
+### 解法
+- 第一步，在每个节点的后面插入复制的节点；
+![random-list-step1.png](/img/random-list-step1.png)
+
+- 第二步，对复制节点的 random 链接进行赋值；
+![random-list-step2.png](/img/random-list-step2.png)
+
+- 第三步，分离两个链表。
+![random-list-step3.png](/img/random-list-step3.png)
+
+```java
+/**
+ * Definition for singly-linked list with a random pointer.
+ * class RandomListNode {
+ *     int label;
+ *     RandomListNode next, random;
+ *     RandomListNode(int x) { this.label = x; }
+ * };
+ */
+public class Solution {
+    public RandomListNode copyRandomList(RandomListNode head) {
+        if (head == null) {
+            return null;
+        }
+        
+        // step1
+        RandomListNode cur = head;
+        while (cur != null) {
+            RandomListNode node = new RandomListNode(cur.label);
+            node.next = cur.next;
+            cur.next = node;
+            cur = node.next;
+        }
+        
+        // step2
+        cur = head;
+        while (cur != null) {
+            RandomListNode clone = cur.next;
+            if (cur.random != null) {
+                clone.random = cur.random.next;   
+            }
+            cur = clone.next;
+        }
+        
+        // step3
+        cur = head;
+        RandomListNode cloneHead = head.next;
+        while (cur.next != null) {
+            RandomListNode clone = cur.next;
+            cur.next = clone.next;
+            cur = clone;
+        }
+        
+        return cloneHead;
+    }
+}
+```

img/random-list-step2.png

@@ -0,0 +1,45 @@
+/**
+ * Definition for singly-linked list with a random pointer.
+ * class RandomListNode {
+ *     int label;
+ *     RandomListNode next, random;
+ *     RandomListNode(int x) { this.label = x; }
+ * };
+ */
+public class Solution {
+    public RandomListNode copyRandomList(RandomListNode head) {
+        if (head == null) {
+            return null;
+        }
+        
+        // step1
+        RandomListNode cur = head;
+        while (cur != null) {
+            RandomListNode node = new RandomListNode(cur.label);
+            node.next = cur.next;
+            cur.next = node;
+            cur = node.next;
+        }
+        
+        // step2
+        cur = head;
+        while (cur != null) {
+            RandomListNode clone = cur.next;
+            if (cur.random != null) {
+                clone.random = cur.random.next;   
+            }
+            cur = clone.next;
+        }
+        
+        // step3
+        cur = head;
+        RandomListNode cloneHead = head.next;
+        while (cur.next != null) {
+            RandomListNode clone = cur.next;
+            cur.next = clone.next;
+            cur = clone;
+        }
+        
+        return cloneHead;
+    }
+}