feat: add the solution of Valid Palindrome II(680) with Java.

Author: Mukyu

README.md

@@ -71,7 +71,7 @@
 | [669][669-question] | [Trim a Binary Search Tree][669-tips]                        | [✅][669-java] | [✅][669-js] |                  |
 | [671][671-question] | [Second Minimum Node In a Binary Tree][671-tips]             | [✅][671-java] | [✅][671-js] |                  |
 | [674][674-question] | [Longest Continuous Increasing Subsequence][674-tips]        | [✅][674-java] | [✅][674-js] |                  |
-| [680][680-question] | [Valid Palindrome II][680-tips]                              |                | [✅][680-js] |                  |
+| [680][680-question] | [Valid Palindrome II][680-tips]                              | [✅][680-java] | [✅][680-js] |                  |
 | [682][682-question] | [Baseball Game][682-tips]                                    |                | [✅][682-js] |                  |
 | [686][686-question] | [Repeated String Match][686-tips]                            |                | [✅][686-js] |                  |
 | [687][687-question] | [Longest Univalue Path][687-tips]                            |                | [✅][687-js] |                  |
@@ -464,6 +464,7 @@
 [669-java]: ./src/_669/Solution.java
 [671-java]: ./src/_671/Solution.java
 [674-java]: ./src/_674/Solution.java
+[680-java]: ./src/_680/Solution.java
 [728-java]: ./src/_728/Solution.java
 [771-java]: ./src/_771/Solution.java
 [804-java]: ./src/_804/Solution.java

src/_680/Solution.java

@@ -0,0 +1,34 @@
+package _680;
+
+class Solution {
+    public boolean validPalindrome(String s) {
+        int l = 0;
+        int r = s.length() - 1;
+        while (l < r) {
+            if (s.charAt(l) != s.charAt(r)) {
+                return isPalindrome(s, l + 1, r) || isPalindrome(s, l, r - 1);
+            }
+            l++;
+            r--;
+        }
+        return l >= r;
+    }
+
+    private boolean isPalindrome(String s, int l, int r) {
+        while (l < r) {
+            if (s.charAt(l) != s.charAt(r)) {
+                return false;
+            }
+            l++;
+            r--;
+        }
+        return true;
+    }
+
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        System.out.println(solution.validPalindrome("aba"));
+        System.out.println(solution.validPalindrome("abca"));
+        System.out.println(solution.validPalindrome("ececcec"));
+    }
+}

tips/680/README.md

@@ -1,46 +1,66 @@
-[xxxx][title]
+[Valid Palindrome II][title]
 
 ## Description
-// 抄题目
+Given a non-empty string `s`, you may delete **at most** one character. Judge whether you can make it a palindrome.
 
+**Example 1:**
 
-**Example:**
+```
+Input: "aba"
+Output: True
+```
+
+**Example 2:**
 
 ```
-// 抄Example
+Input: "abca"
+Output: True
+Explanation: You could delete the character 'c'.
 ```
 
 **Note:**
-// Note
 
-**Tags:** // tags
+1. The string will only contain lowercase characters a-z. The maximum length of the string is 50000.
 
+**Tags:** [String](https://leetcode.com/tag/string/)
 
-## 思路 1
-// 贴一些关键代码,说一些解题思路
-// (同一种语言可以写多种思路，与某种语言思路相同的另一种语言的思路无须赘述，但可以把代码贴在后面) 
-```java
+## 思路
 
-```
-```javascript
+给出一个字符串，要求判断是否可以通过删除最多一个字符来使得原字符串变成回文字符串。对原字符串进行回文判断，若发现左右不匹配的情况下，尝试删除左边或右边的字符，再进行判断，只要其中一种删除方式能使原字符串成为回文字符串则判断可行，若两种删除方式均不行则判断为不可行。
 
-```
+**Java:**
 
-## 思路 2
-// 贴一些关键代码,说一些解题思路
 ```java
-
-```
-
-## 思路 3
-// 贴一些关键代码,说一些解题思路
-```kotlin
-
+class Solution {
+    public boolean validPalindrome(String s) {
+        int l = 0;
+        int r = s.length() - 1;
+        while (l < r) {
+            if (s.charAt(l) != s.charAt(r)) {
+                return isPalindrome(s, l + 1, r) || isPalindrome(s, l, r - 1);
+            }
+            l++;
+            r--;
+        }
+        return l >= r;
+    }
+
+    private boolean isPalindrome(String s, int l, int r) {
+        while (l < r) {
+            if (s.charAt(l) != s.charAt(r)) {
+                return false;
+            }
+            l++;
+            r--;
+        }
+        return true;
+    }
+}
 ```
 
 ## 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
+[title]: https://leetcode.com/problems/valid-palindrome-ii/description/
 [ls]: https://github.com/SDE603/LeetCode-Solution