diff --git a/src/main/java/leetcode/editor/cn/FindTheDifference.java b/src/main/java/leetcode/editor/cn/FindTheDifference.java
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+//给定两个字符串 s 和 t ，它们只包含小写字母。 
+//
+// 字符串 t 由字符串 s 随机重排，然后在随机位置添加一个字母。 
+//
+// 请找出在 t 中被添加的字母。 
+//
+// 
+//
+// 示例 1： 
+//
+// 
+//输入：s = "abcd", t = "abcde"
+//输出："e"
+//解释：'e' 是那个被添加的字母。
+// 
+//
+// 示例 2： 
+//
+// 
+//输入：s = "", t = "y"
+//输出："y"
+// 
+//
+// 
+//
+// 提示： 
+//
+// 
+// 0 <= s.length <= 1000 
+// t.length == s.length + 1 
+// s 和 t 只包含小写字母 
+// 
+// Related Topics 位运算 哈希表 字符串 排序 👍 309 👎 0
+
+package leetcode.editor.cn;
+
+//389:找不同
+public class FindTheDifference{
+    public static void main(String[] args) {
+        Solution solution = new FindTheDifference().new Solution();
+        
+    }
+
+//leetcode submit region begin(Prohibit modification and deletion)
+class Solution {
+    public char findTheDifference(String s, String t) {
+        int[] chs = new int[26];
+        for (char ch:s.toCharArray()){
+            chs[ch-'a']++;
+        }
+        for (char ch:t.toCharArray()){
+            if(chs[ch-'a']==0){
+                return ch;
+            }
+            chs[ch-'a']--;
+        }
+        return 'a';
+    }
+}
+//leetcode submit region end(Prohibit modification and deletion)
+
+}
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diff --git a/src/main/java/leetcode/editor/cn/doc/content/FindTheDifference.md b/src/main/java/leetcode/editor/cn/doc/content/FindTheDifference.md
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+<p>给定两个字符串 <code>s</code> 和 <code>t</code>&nbsp;，它们只包含小写字母。</p>
+
+<p>字符串 <code>t</code>&nbsp;由字符串 <code>s</code> 随机重排，然后在随机位置添加一个字母。</p>
+
+<p>请找出在 <code>t</code>&nbsp;中被添加的字母。</p>
+
+<p>&nbsp;</p>
+
+<p><strong>示例 1：</strong></p>
+
+<pre>
+<strong>输入：</strong>s = "abcd", t = "abcde"
+<strong>输出：</strong>"e"
+<strong>解释：</strong>'e' 是那个被添加的字母。
+</pre>
+
+<p><strong>示例 2：</strong></p>
+
+<pre>
+<strong>输入：</strong>s = "", t = "y"
+<strong>输出：</strong>"y"
+</pre>
+
+<p>&nbsp;</p>
+
+<p><strong>提示：</strong></p>
+
+<ul>
+	<li><code>0 &lt;= s.length &lt;= 1000</code></li>
+	<li><code>t.length == s.length + 1</code></li>
+	<li><code>s</code> 和 <code>t</code> 只包含小写字母</li>
+</ul>
+<div><div>Related Topics</div><div><li>位运算</li><li>哈希表</li><li>字符串</li><li>排序</li></div></div><br><div><li>👍 309</li><li>👎 0</li></div>
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