diff --git a/src/main/java/leetcode/editor/cn/LongestSubstringWithAtMostTwoDistinctCharacters.java b/src/main/java/leetcode/editor/cn/LongestSubstringWithAtMostTwoDistinctCharacters.java
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index 0000000..749df1a
--- /dev/null
+++ b/src/main/java/leetcode/editor/cn/LongestSubstringWithAtMostTwoDistinctCharacters.java
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+//给定一个字符串 s ，找出 至多 包含两个不同字符的最长子串 t ，并返回该子串的长度。 
+//
+// 示例 1: 
+//
+// 输入: "eceba"
+//输出: 3
+//解释: t 是 "ece"，长度为3。
+// 
+//
+// 示例 2: 
+//
+// 输入: "ccaabbb"
+//输出: 5
+//解释: t 是 "aabbb"，长度为5。
+// 
+// Related Topics 哈希表 字符串 滑动窗口 👍 132 👎 0
+
+package leetcode.editor.cn;
+
+import java.util.*;
+
+//159:至多包含两个不同字符的最长子串
+class LongestSubstringWithAtMostTwoDistinctCharacters {
+    public static void main(String[] args) {
+        //测试代码
+        Solution solution = new LongestSubstringWithAtMostTwoDistinctCharacters().new Solution();
+    }
+
+    //力扣代码
+    //leetcode submit region begin(Prohibit modification and deletion)
+    class Solution {
+        public int lengthOfLongestSubstringTwoDistinct(String s) {
+            int n = s.length();
+            if (n < 3) return n;
+            int left = 0;
+            int right = 0;
+            Map<Character, Integer> hashmap = new HashMap<>();
+
+            int max_len = 2;
+
+            while (right < n) {
+                if (hashmap.size() < 3)
+                    hashmap.put(s.charAt(right), right++);
+                if (hashmap.size() == 3) {
+                    int del_idx = Collections.min(hashmap.values());
+                    hashmap.remove(s.charAt(del_idx));
+                    // move left pointer of the slidewindow
+                    left = del_idx + 1;
+                }
+
+                max_len = Math.max(max_len, right - left);
+            }
+            return max_len;
+
+        }
+    }
+//leetcode submit region end(Prohibit modification and deletion)
+
+}
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diff --git a/src/main/java/leetcode/editor/cn/doc/content/LongestSubstringWithAtMostTwoDistinctCharacters.md b/src/main/java/leetcode/editor/cn/doc/content/LongestSubstringWithAtMostTwoDistinctCharacters.md
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+++ b/src/main/java/leetcode/editor/cn/doc/content/LongestSubstringWithAtMostTwoDistinctCharacters.md
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+<p>给定一个字符串<strong><em> s</em></strong> ，找出&nbsp;<strong>至多&nbsp;</strong>包含两个不同字符的最长子串 <strong><em>t</em> </strong>，并返回该子串的长度。</p>
+
+<p><strong>示例 1:</strong></p>
+
+<pre><strong>输入:</strong> &quot;eceba&quot;
+<strong>输出: </strong>3
+<strong>解释: <em>t</em></strong> 是 &quot;ece&quot;，长度为3。
+</pre>
+
+<p><strong>示例 2:</strong></p>
+
+<pre><strong>输入:</strong> &quot;ccaabbb&quot;
+<strong>输出: </strong>5
+<strong>解释: <em>t</em></strong><em> </em>是 &quot;aabbb&quot;，长度为5。
+</pre>
+<div><div>Related Topics</div><div><li>哈希表</li><li>字符串</li><li>滑动窗口</li></div></div><br><div><li>👍 132</li><li>👎 0</li></div>
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