diff --git a/CHANGELOG.md b/CHANGELOG.md
index 24138178..6914257e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.2.7] - 2021-02-09
+### Changed
+- Optimize PriorityQueue<TKey, TValue>
+
 ## [1.2.6] - 2021-02-09
 ### Added
 - Add PriorityQueue.TryDequeue
diff --git a/Directory.Build.props b/Directory.Build.props
index 1be78654..d30fa0f8 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -7,8 +7,8 @@
     <RepositoryUrl>https://github.com/naminodarie/ac-library-csharp</RepositoryUrl>
     <PackageReleaseNotes>https://github.com/naminodarie/ac-library-csharp/blob/master/CHANGELOG.md</PackageReleaseNotes>
 
-    <Version>1.2.6</Version>
-    <AssemblyVersion>1.2.6.100</AssemblyVersion>
+    <Version>1.2.7</Version>
+    <AssemblyVersion>1.2.7.100</AssemblyVersion>
     <RepositoryCommit Condition="'$(GIT_COMMIT)' != ''">$(GIT_COMMIT)</RepositoryCommit>
 
     <SignAssembly>True</SignAssembly>
diff --git a/Source/AtCoderLibrary/STL/Internal/IPriorityQueueOp.cs b/Source/AtCoderLibrary/STL/Internal/IPriorityQueueOp.cs
new file mode 100644
index 00000000..1f0cbd8b
--- /dev/null
+++ b/Source/AtCoderLibrary/STL/Internal/IPriorityQueueOp.cs
@@ -0,0 +1,12 @@
+namespace AtCoder.Internal
+{
+    public interface IPriorityQueueOp<T>
+    {
+        int Count { get; }
+        T Peek { get; }
+        void Add(T value);
+        T Dequeue();
+        bool TryDequeue(out T result);
+        void Clear();
+    }
+}
diff --git a/Source/AtCoderLibrary/STL/Internal/PriorityQueueOp.cs b/Source/AtCoderLibrary/STL/Internal/PriorityQueueOp.cs
index 9cbf644a..59250c2c 100644
--- a/Source/AtCoderLibrary/STL/Internal/PriorityQueueOp.cs
+++ b/Source/AtCoderLibrary/STL/Internal/PriorityQueueOp.cs
@@ -1,12 +1,15 @@
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Runtime.CompilerServices;
 
 namespace AtCoder.Internal
 {
+    [DebuggerTypeProxy(typeof(PriorityQueueOp<,>.DebugView))]
     [DebuggerDisplay("Count = {" + nameof(Count) + "}")]
-    public class PriorityQueueOp<T, TOp> where TOp : IComparer<T>
+    public class PriorityQueueOp<T, TOp> : IPriorityQueueOp<T>, IEnumerable
+        where TOp : IComparer<T>
     {
         protected T[] data;
         protected readonly TOp _comparer;
@@ -88,16 +91,23 @@ protected internal void UpdateDown(int i)
             data[i] = tar;
         }
         public void Clear() => Count = 0;
-        [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
-        [System.Diagnostics.CodeAnalysis.SuppressMessage("CodeQuality", "IDE0051", Justification = "for debugger")]
-        private T[] Items
+
+        private T[] GetItems()
+        {
+            var arr = new ArraySegment<T>(data, 0, Count).ToArray();
+            Array.Sort(arr, _comparer);
+            return arr;
+        }
+        IEnumerator IEnumerable.GetEnumerator() => GetItems().GetEnumerator();
+        private class DebugView
         {
-            get
+            private readonly PriorityQueueOp<T, TOp> pq;
+            public DebugView(PriorityQueueOp<T, TOp> pq)
             {
-                var arr = new ArraySegment<T>(data, 0, Count).ToArray();
-                Array.Sort(arr, _comparer);
-                return arr;
+                this.pq = pq;
             }
+            [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+            public T[] Items => pq.GetItems();
         }
     }
 }
diff --git a/Source/AtCoderLibrary/STL/Internal/PriorityQueueOp`2.cs b/Source/AtCoderLibrary/STL/Internal/PriorityQueueOp`2.cs
index 9469ad59..6020e735 100644
--- a/Source/AtCoderLibrary/STL/Internal/PriorityQueueOp`2.cs
+++ b/Source/AtCoderLibrary/STL/Internal/PriorityQueueOp`2.cs
@@ -1,21 +1,52 @@
-using System.Collections.Generic;
+using System;
+using System.Collections;
+using System.Collections.Generic;
 using System.Diagnostics;
 using System.Runtime.CompilerServices;
 
 namespace AtCoder.Internal
 {
+    [DebuggerTypeProxy(typeof(PriorityQueueOp<,,>.DebugView))]
     [DebuggerDisplay("Count = {" + nameof(Count) + "}")]
-    public class PriorityQueueOp<TKey, TValue, TKOp>
-        : PriorityQueueOp<KeyValuePair<TKey, TValue>, KeyComparer<TKey, TValue, TKOp>>
+    public class PriorityQueueOp<TKey, TValue, TKOp> :
+        IPriorityQueueOp<KeyValuePair<TKey, TValue>>, IEnumerable
         where TKOp : IComparer<TKey>
     {
+        protected TKey[] keys;
+        protected TValue[] values;
+        protected readonly TKOp _comparer;
+        internal const int DefaultCapacity = 16;
         public PriorityQueueOp() : this(default(TKOp)) { }
         public PriorityQueueOp(int capacity) : this(capacity, default(TKOp)) { }
-        public PriorityQueueOp(TKOp comparer) : base(new KeyComparer<TKey, TValue, TKOp>(comparer)) { }
-        public PriorityQueueOp(int capacity, TKOp comparer) : base(capacity, new KeyComparer<TKey, TValue, TKOp>(comparer)) { }
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public void Add(TKey key, TValue value) => Add(new KeyValuePair<TKey, TValue>(key, value));
+        public PriorityQueueOp(TKOp comparer) : this(DefaultCapacity, comparer) { }
+        public PriorityQueueOp(int capacity, TKOp comparer)
+        {
+            if (comparer == null)
+                throw new ArgumentNullException(nameof(comparer));
+            keys = new TKey[Math.Max(capacity, DefaultCapacity)];
+            values = new TValue[Math.Max(capacity, DefaultCapacity)];
+            _comparer = comparer;
+        }
+        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
+        public int Count { get; private set; } = 0;
 
+        public KeyValuePair<TKey, TValue> Peek => KeyValuePair.Create(keys[0], values[0]);
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal void Resize()
+        {
+            Array.Resize(ref keys, keys.Length << 1);
+            Array.Resize(ref values, values.Length << 1);
+        }
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Add(KeyValuePair<TKey, TValue> pair) => Add(pair.Key, pair.Value);
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Add(TKey key, TValue value)
+        {
+            if (Count >= keys.Length) Resize();
+            keys[Count] = key;
+            values[Count++] = value;
+            UpdateUp(Count - 1);
+        }
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public bool TryDequeue(out TKey key, out TValue value)
         {
@@ -28,5 +59,85 @@ public bool TryDequeue(out TKey key, out TValue value)
             (key, value) = Dequeue();
             return true;
         }
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public bool TryDequeue(out KeyValuePair<TKey, TValue> result)
+        {
+            if (Count == 0)
+            {
+                result = default(KeyValuePair<TKey, TValue>);
+                return false;
+            }
+            result = Dequeue();
+            return true;
+        }
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public KeyValuePair<TKey, TValue> Dequeue()
+        {
+            var res = KeyValuePair.Create(keys[0], values[0]);
+            keys[0] = keys[--Count];
+            values[0] = values[Count];
+            UpdateDown(0);
+            return res;
+        }
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        protected internal void UpdateUp(int i)
+        {
+            var tar = keys[i];
+            var tarVal = values[i];
+            while (i > 0)
+            {
+                var p = (i - 1) >> 1;
+                if (_comparer.Compare(tar, keys[p]) >= 0)
+                    break;
+                keys[i] = keys[p];
+                values[i] = values[p];
+                i = p;
+            }
+            keys[i] = tar;
+            values[i] = tarVal;
+        }
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        protected internal void UpdateDown(int i)
+        {
+            var tar = keys[i];
+            var tarVal = values[i];
+            var n = Count;
+            var child = 2 * i + 1;
+            while (child < n)
+            {
+                if (child != n - 1 && _comparer.Compare(keys[child], keys[child + 1]) > 0) child++;
+                if (_comparer.Compare(tar, keys[child]) <= 0)
+                    break;
+                keys[i] = keys[child];
+                values[i] = values[child];
+                i = child;
+                child = 2 * i + 1;
+            }
+            keys[i] = tar;
+            values[i] = tarVal;
+        }
+        public void Clear() => Count = 0;
+
+        private KeyValuePair<TKey, TValue>[] GetItems()
+        {
+            var keys = new ArraySegment<TKey>(this.keys, 0, Count).ToArray();
+            var values = new ArraySegment<TValue>(this.values, 0, Count).ToArray();
+            Array.Sort(keys, values, _comparer);
+            var arr = new KeyValuePair<TKey, TValue>[Count];
+            for (int i = 0; i < arr.Length; i++)
+                arr[i] = KeyValuePair.Create(keys[i], values[i]);
+            return arr;
+        }
+        IEnumerator IEnumerable.GetEnumerator() => GetItems().GetEnumerator();
+        private class DebugView
+        {
+            private readonly PriorityQueueOp<TKey, TValue, TKOp> pq;
+            public DebugView(PriorityQueueOp<TKey, TValue, TKOp> pq)
+            {
+                this.pq = pq;
+            }
+            [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+            public KeyValuePair<TKey, TValue>[] Items => pq.GetItems();
+        }
     }
 }