From ea4d1c73364fa09e8d5c621b03b95d51166d212e Mon Sep 17 00:00:00 2001
From: Matthew Parkinson <parky@outlook.com>
Date: Thu, 22 Sep 2016 13:20:11 +0100
Subject: [PATCH 1/2] Fixed performance of Min/Max in SortedSet.

The existing implementation of Min/Max calls InOrderWalkTree,
which perform an allocation of a stack for traversing the tree.
But when you are finding the smallest or largest element in a
tree there is no need to perform this allocation.  This is an
optimised version that directly finds the smallest or largest
element.
---
 .../System/Collections/Generic/SortedSet.cs   | 30 +++++++++++++++----
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/src/System.Collections/src/System/Collections/Generic/SortedSet.cs b/src/System.Collections/src/System/Collections/Generic/SortedSet.cs
index b1febacf1cc3..dba35b573248 100644
--- a/src/System.Collections/src/System/Collections/Generic/SortedSet.cs
+++ b/src/System.Collections/src/System/Collections/Generic/SortedSet.cs
@@ -1845,9 +1845,18 @@ public T Min
         {
             get
             {
-                T ret = default(T);
-                InOrderTreeWalk(delegate (SortedSet<T>.Node n) { ret = n.Item; return false; });
-                return ret;
+                if (_root == null)
+                {
+                    return default(T);
+                }
+
+                var current = _root;
+                while (current.Left != null)
+                {
+                    current = current.Left;
+                }
+
+                return current.Item;
             }
         }
 
@@ -1855,9 +1864,18 @@ public T Max
         {
             get
             {
-                T ret = default(T);
-                InOrderTreeWalk(delegate (SortedSet<T>.Node n) { ret = n.Item; return false; }, true);
-                return ret;
+                if (_root == null)
+                {
+                    return default(T);
+                }
+
+                var current = _root;
+                while (current.Right != null)
+                {
+                    current = current.Right;
+                }
+
+                return current.Item;
             }
         }
 

From af7cc0de2e95a515d032020d48c24de5a5854e63 Mon Sep 17 00:00:00 2001
From: Matthew Parkinson <parky@outlook.com>
Date: Thu, 22 Sep 2016 16:02:20 +0100
Subject: [PATCH 2/2] Code review feedback

---
 .../src/System/Collections/Generic/SortedSet.cs               | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/System.Collections/src/System/Collections/Generic/SortedSet.cs b/src/System.Collections/src/System/Collections/Generic/SortedSet.cs
index dba35b573248..df67684635c4 100644
--- a/src/System.Collections/src/System/Collections/Generic/SortedSet.cs
+++ b/src/System.Collections/src/System/Collections/Generic/SortedSet.cs
@@ -1850,7 +1850,7 @@ public T Min
                     return default(T);
                 }
 
-                var current = _root;
+                Node current = _root;
                 while (current.Left != null)
                 {
                     current = current.Left;
@@ -1869,7 +1869,7 @@ public T Max
                     return default(T);
                 }
 
-                var current = _root;
+                Node current = _root;
                 while (current.Right != null)
                 {
                     current = current.Right;