Fix a performance regression.

Add test.

Author: skexzeal

NetDiff.Test/Test.cs

@@ -556,6 +556,66 @@ public void SpecifiedComparer()
             Assert.AreEqual(DiffStatus.Inserted, results.ElementAt(4).Status);
         }
 
+        [TestMethod]
+        public void CaseReplace()
+        {
+            string str1 = "abbbc";
+            string str2 = "adbbc";
+
+            var option = DiffOption<char>.Default;
+            option.Order = DiffOrder.GreedyDeleteFirst;
+
+            var results = DiffUtil.Diff(str1, str2, option);
+
+            Assert.AreEqual(DiffStatus.Equal, results.ElementAt(0).Status);
+            Assert.AreEqual(DiffStatus.Deleted, results.ElementAt(1).Status);
+            Assert.AreEqual(DiffStatus.Inserted, results.ElementAt(2).Status);
+            Assert.AreEqual(DiffStatus.Equal, results.ElementAt(3).Status);
+            Assert.AreEqual(DiffStatus.Equal, results.ElementAt(4).Status);
+            Assert.AreEqual(DiffStatus.Equal, results.ElementAt(5).Status);
+        }
+
+        [TestMethod]
+        public void GivenEmpty()
+        {
+            string str1 = "";
+            string str2 = "";
+
+            var results = DiffUtil.Diff(str1, str2);
+
+            Assert.IsTrue(!results.Any());
+        }
+
+        [TestMethod]
+        public void GivenSeq1Empty()
+        {
+            string str1 = "";
+            string str2 = "abcde";
+
+            var results = DiffUtil.Diff(str1, str2);
+
+            Assert.AreEqual(DiffStatus.Inserted, results.ElementAt(0).Status);
+            Assert.AreEqual(DiffStatus.Inserted, results.ElementAt(1).Status);
+            Assert.AreEqual(DiffStatus.Inserted, results.ElementAt(2).Status);
+            Assert.AreEqual(DiffStatus.Inserted, results.ElementAt(3).Status);
+            Assert.AreEqual(DiffStatus.Inserted, results.ElementAt(4).Status);
+        }
+
+        [TestMethod]
+        public void GivenSeq2Empty()
+        {
+            string str1 = "abced";
+            string str2 = "";
+
+            var results = DiffUtil.Diff(str1, str2);
+
+            Assert.AreEqual(DiffStatus.Deleted, results.ElementAt(0).Status);
+            Assert.AreEqual(DiffStatus.Deleted, results.ElementAt(1).Status);
+            Assert.AreEqual(DiffStatus.Deleted, results.ElementAt(2).Status);
+            Assert.AreEqual(DiffStatus.Deleted, results.ElementAt(3).Status);
+            Assert.AreEqual(DiffStatus.Deleted, results.ElementAt(4).Status);
+        }
+
         [TestMethod]
         public void Performance()
         {
@@ -579,6 +639,23 @@ public void Performance()
             Assert.IsTrue(time2 < time1);
         }
 
+        [TestMethod]
+        public void Performance2()
+        {
+            var str1 = Enumerable.Repeat("good dog", 1000000).SelectMany(c => c);
+            var str2 = Enumerable.Repeat("Bad dog", 1000000).SelectMany(c => c);
+
+            var option = DiffOption<char>.Default;
+            option.Limit = 100;
+            var sw = new System.Diagnostics.Stopwatch();
+            sw.Start();
+            var result1 = DiffUtil.Diff(str1, str2, option);
+            sw.Stop();
+            var time1 = sw.Elapsed.TotalSeconds;
+
+            System.Console.WriteLine(sw.Elapsed.TotalSeconds);
+        }
+
         [TestMethod]
         public void CaseEmpty()
         {

NetDiff/EditGraph.cs

@@ -93,6 +93,12 @@ public EditGraph(
 
         public List<Point> CalculatePath(DiffOption<T> option)
         {
+            if (!seq1.Any())
+                return Enumerable.Range(0, seq2.Length + 1).Select(i => new Point(0, i)).ToList();
+
+            if (!seq2.Any())
+                return Enumerable.Range(0, seq1.Length + 1).Select(i => new Point(i, 0)).ToList();
+
             this.option = option;
 
             BeginCalculatePath();
@@ -152,7 +158,7 @@ private void UpdateHeads()
             if (option.Limit > 0 && heads.Count > option.Limit)
             {
                 var selectedNode = SelectNode(heads);
-                Initialize();
+                heads.Clear();
                 heads.Add(selectedNode);
             }