feat: add the solution of Linked List Cycle(141) with java.

Author: relish-wang

README.md

@@ -87,6 +87,7 @@
 | [122][122-question] | [Best Time to Buy and Sell Stock II][122-tips]               | [Easy][E]   | [✅][122-java] |              | [✅][122-kotlin] |
 | [125][125-question] | [Valid Palindrome][125-tips]                                 | [Easy][E]   |                |              | [✅][125-kotlin] |
 | [136][136-question] | [Single Number][136-tips]                                    | [Easy][E]   |                |              | [✅][136-kotlin] |
+| [141][141-question] | [Linked List Cycle][141-tips]                                | [Easy][E]   | [✅][141-java] |              |                  |
 | [226][226-question] | [Invert Binary Tree][226-tips]                               | [Easy][E]   | [✅][226-java] | [✅][226-js] | [✅][226-kotlin] |
 | [504][504-question] | [Base 7][504-tips]                                           | [Easy][E]   |                |              | [✅][504-kotlin] |
 | [543][543-question] | [Diameter of Binary Tree][543-tips]                          | [Easy][E]   | [✅][543-java] |              | [✅][543-kotlin] |
@@ -310,6 +311,7 @@
 [122-tips]: ./tips/122/README.md
 [125-tips]: ./tips/125/README.md
 [136-tips]: ./tips/136/README.md
+[141-tips]: ./tips/141/README.md
 [226-tips]: ./tips/226/README.md
 [504-tips]: ./tips/504/README.md
 [543-tips]: ./tips/543/README.md
@@ -461,6 +463,7 @@
 [119-java]: ./src/_119/Solution.java
 [121-java]: ./src/_121/Solution.java
 [122-java]: ./src/_122/Solution.java
+[141-java]: ./src/_141/Solution.java
 [226-java]: ./src/_226/Solution.java
 [543-java]: ./src/_543/Solution.java
 [554-java]: ./src/_554/Solution.java

src/_141/Solution.java

@@ -0,0 +1,38 @@
+package _141;
+
+import structure.ListNode;
+
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ * int val;
+ * ListNode next;
+ * ListNode(int x) {
+ * val = x;
+ * next = null;
+ * }
+ * }
+ *
+ * @author relish
+ * @since 2018/11/15
+ */
+public class Solution {
+
+    public boolean hasCycle(ListNode head) {
+        ListNode fast = head, slow = head;
+        if (fast == null) return false;
+        while (slow != null && fast.next != null) {
+            slow = slow.next;
+            fast = fast.next.next;
+            if (slow == fast) {
+                return true;
+            }
+            if (fast == null) break;
+        }
+        return false;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(new Solution().hasCycle(ListNode.createTestData("[1,2]")));
+    }
+}

tips/141/README.md

@@ -0,0 +1,42 @@
+[Linked List Cycle][title]
+
+## Description
+Given a linked list, determine if it has a cycle in it.
+
+Follow up:
+Can you solve it without using extra space?
+
+
+**Tags:** 
+Linked List、Two Pointers
+
+
+## 思路
+
+java(0ms/100.00%): 
+简单举个例子, 两个人在田径场上绕圈跑步, A的速度为1, B的速度为2, 总有某个时刻, B会追上A。(B和A在同一个位置)
+```java
+public class Solution {
+
+    public boolean hasCycle(ListNode head) {
+        ListNode fast = head, slow = head;
+        if (fast == null) return false;
+        while (slow != null && fast.next != null) {
+            slow = slow.next;
+            fast = fast.next.next;
+            if (slow == fast) {
+                return true;
+            }
+            if (fast == null) break;
+        }
+        return false;
+    }
+}
+```
+
+## 结语
+   
+如果你同我们一样热爱数据结构、算法、LeetCode，可以关注我们 GitHub 上的 LeetCode 题解：[LeetCode-Solution][ls]
+
+[title]: https://leetcode.com/problems/xxxx
+[ls]: https://github.com/RichCodersAndMe/LeetCode-Solution