From 6865c7a2389c9f90c281576eb98b53e89aac3d74 Mon Sep 17 00:00:00 2001
From: Ivandro Ismael <ivandrofly@gmail.com>
Date: Thu, 24 Nov 2016 18:05:57 +0000
Subject: [PATCH] [Utilities] - Optimize ReverseParenthesis.

---
 libse/Utilities.cs | 40 +++++++++++++++++++++++++++++-----------
 1 file changed, 29 insertions(+), 11 deletions(-)

diff --git a/libse/Utilities.cs b/libse/Utilities.cs
index f54e9c3a4..b60d348f5 100644
--- a/libse/Utilities.cs
+++ b/libse/Utilities.cs
@@ -1218,17 +1218,35 @@ namespace Nikse.SubtitleEdit.Core
 
         private static string ReverseParenthesis(string s)
         {
-            const string k = "@__<<>___@";
-
-            s = s.Replace("(", k);
-            s = s.Replace(')', '(');
-            s = s.Replace(k, ")");
-
-            s = s.Replace("[", k);
-            s = s.Replace(']', '[');
-            s = s.Replace(k, "]");
-
-            return s;
+            if (string.IsNullOrEmpty(s))
+            {
+                return s;
+            }
+            int len = s.Length;
+            char[] chars = new char[len];
+            // O(n)
+            for (int i = len - 1; i >= 0; i--)
+            {
+                char ch = s[i];
+                if (ch == '(')
+                {
+                    ch = ')';
+                }
+                else if (ch == ')')
+                {
+                    ch = '(';
+                }
+                else if (ch == '[')
+                {
+                    ch = ']';
+                }
+                else if (ch == ']')
+                {
+                    ch = '[';
+                }
+                chars[i] = ch;
+            }
+            return new string(chars);
         }
 
         public static string FixEnglishTextInRightToLeftLanguage(string text, string reverseChars)