diff --git a/.idea/.idea.Leetcode/.idea/workspace.xml b/.idea/.idea.Leetcode/.idea/workspace.xml
index 1c355c4..6fcef90 100644
--- a/.idea/.idea.Leetcode/.idea/workspace.xml
+++ b/.idea/.idea.Leetcode/.idea/workspace.xml
@@ -89,11 +89,9 @@
   </component>
   <component name="ChangeListManager">
     <list default="true" id="11f2de1c-1ee5-4aa4-91e6-11975ebd421f" name="Changes" comment="">
-      <change afterPath="$PROJECT_DIR$/451. Sort Characters By Frequency/451. Sort Characters By Frequency.csproj" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/451. Sort Characters By Frequency/Program.cs" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/451. Sort Characters By Frequency/Solution.cs" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/451. Sort Characters By Frequency/Fast/FastSolution.cs" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/.idea/.idea.Leetcode/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/.idea.Leetcode/.idea/workspace.xml" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/Leetcode.sln" beforeDir="false" afterPath="$PROJECT_DIR$/Leetcode.sln" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/451. Sort Characters By Frequency/Program.cs" beforeDir="false" afterPath="$PROJECT_DIR$/451. Sort Characters By Frequency/Program.cs" afterDir="false" />
     </list>
     <option name="SHOW_DIALOG" value="false" />
     <option name="HIGHLIGHT_CONFLICTS" value="true" />
@@ -125,33 +123,34 @@
     <option name="hideEmptyMiddlePackages" value="true" />
     <option name="showLibraryContents" value="true" />
   </component>
-  <component name="PropertiesComponent">{
-  &quot;keyToString&quot;: {
-    &quot;.NET Project.14. Longest Common Prefix.executor&quot;: &quot;Run&quot;,
-    &quot;.NET Project.150. Evaluate Reverse Polish Notation.executor&quot;: &quot;Run&quot;,
-    &quot;.NET Project.9. Palindrome Number.executor&quot;: &quot;Run&quot;,
-    &quot;ASKED_ADD_EXTERNAL_FILES&quot;: &quot;true&quot;,
-    &quot;RunOnceActivity.OpenProjectViewOnStart&quot;: &quot;true&quot;,
-    &quot;RunOnceActivity.ShowReadmeOnStart&quot;: &quot;true&quot;,
-    &quot;WebServerToolWindowFactoryState&quot;: &quot;false&quot;,
-    &quot;git-widget-placeholder&quot;: &quot;main&quot;,
-    &quot;last_opened_file_path&quot;: &quot;/home/nullptr/Projects/dotnet/Leetcode/15. 3Sum/15. 3Sum.csproj&quot;,
-    &quot;node.js.detected.package.eslint&quot;: &quot;true&quot;,
-    &quot;node.js.detected.package.tslint&quot;: &quot;true&quot;,
-    &quot;node.js.selected.package.eslint&quot;: &quot;(autodetect)&quot;,
-    &quot;node.js.selected.package.tslint&quot;: &quot;(autodetect)&quot;,
-    &quot;nodejs_package_manager_path&quot;: &quot;npm&quot;,
-    &quot;settings.editor.selected.configurable&quot;: &quot;SolutionBuilderGeneralOptionsPage&quot;,
-    &quot;vue.rearranger.settings.migration&quot;: &quot;true&quot;
+  <component name="PropertiesComponent"><![CDATA[{
+  "keyToString": {
+    ".NET Project.14. Longest Common Prefix.executor": "Run",
+    ".NET Project.150. Evaluate Reverse Polish Notation.executor": "Run",
+    ".NET Project.451. Sort Characters By Frequency.executor": "Run",
+    ".NET Project.9. Palindrome Number.executor": "Run",
+    "ASKED_ADD_EXTERNAL_FILES": "true",
+    "RunOnceActivity.OpenProjectViewOnStart": "true",
+    "RunOnceActivity.ShowReadmeOnStart": "true",
+    "WebServerToolWindowFactoryState": "false",
+    "git-widget-placeholder": "main",
+    "last_opened_file_path": "/home/nullptr/Projects/dotnet/Leetcode/15. 3Sum/15. 3Sum.csproj",
+    "node.js.detected.package.eslint": "true",
+    "node.js.detected.package.tslint": "true",
+    "node.js.selected.package.eslint": "(autodetect)",
+    "node.js.selected.package.tslint": "(autodetect)",
+    "nodejs_package_manager_path": "npm",
+    "settings.editor.selected.configurable": "SolutionBuilderGeneralOptionsPage",
+    "vue.rearranger.settings.migration": "true"
   },
-  &quot;keyToStringList&quot;: {
-    &quot;rider.external.source.directories&quot;: [
-      &quot;/home/nullptr/.config/JetBrains/Rider2023.3/resharper-host/DecompilerCache&quot;,
-      &quot;/home/nullptr/.config/JetBrains/Rider2023.3/resharper-host/SourcesCache&quot;,
-      &quot;/home/nullptr/.local/share/Symbols/src&quot;
+  "keyToStringList": {
+    "rider.external.source.directories": [
+      "/home/nullptr/.config/JetBrains/Rider2023.3/resharper-host/DecompilerCache",
+      "/home/nullptr/.config/JetBrains/Rider2023.3/resharper-host/SourcesCache",
+      "/home/nullptr/.local/share/Symbols/src"
     ]
   }
-}</component>
+}]]></component>
   <component name="RunManager" selected=".NET Project.451. Sort Characters By Frequency">
     <configuration name="101. Symmetric Tree" type="DotNetProject" factoryName=".NET Project">
       <option name="EXE_PATH" value="" />
@@ -1702,7 +1701,7 @@
       <workItem from="1678030078340" duration="114000" />
       <workItem from="1680804946367" duration="3697000" />
       <workItem from="1706644472303" duration="7903000" />
-      <workItem from="1707331420927" duration="422000" />
+      <workItem from="1707331420927" duration="1097000" />
     </task>
     <servers />
   </component>
diff --git a/451. Sort Characters By Frequency/Fast/FastSolution.cs b/451. Sort Characters By Frequency/Fast/FastSolution.cs
new file mode 100644
index 0000000..b024f3b
--- /dev/null
+++ b/451. Sort Characters By Frequency/Fast/FastSolution.cs	
@@ -0,0 +1,26 @@
+using System.Text;
+
+namespace _451._Sort_Characters_By_Frequency.Fast;
+
+public class Solution
+{
+    private static int Comparer((char, int) el1, (char, int) el2)
+    {
+        return el2.Item2.CompareTo(el1.Item2);
+    }
+    
+    public string FrequencySort(string s)
+    {
+        var count = new (char, int)[128];
+        for (var ch = (char)0; ch < count.Length; ch++)
+            count[ch].Item1 = ch;
+        foreach (var c in s)
+            count[c].Item2++;
+        var sb = new StringBuilder();
+        Array.Sort(count, Comparer);
+        for (var ch = (char)0; ch < count.Length; ch++)
+            while (count[ch].Item2-- > 0)
+                sb.Append(count[ch].Item1);
+        return sb.ToString();
+    }
+}
\ No newline at end of file
diff --git a/451. Sort Characters By Frequency/Program.cs b/451. Sort Characters By Frequency/Program.cs
index 9967c7b..04fb8eb 100644
--- a/451. Sort Characters By Frequency/Program.cs	
+++ b/451. Sort Characters By Frequency/Program.cs	
@@ -1,4 +1,4 @@
 using _451._Sort_Characters_By_Frequency;
 
-var sol = new Solution();
+var sol = new _451._Sort_Characters_By_Frequency.Fast.Solution();
 Console.WriteLine(sol.FrequencySort("gbngjaaaaaaaafsdgnjk;fdsnjkg;fds"));
\ No newline at end of file