Add two leetcode solutions - leetcode38 and leetcode 163.

Author: yanglr

.vs/ProjectSettings.json

@@ -0,0 +1,3 @@
+{
+  "CurrentProjectSetting": null
+}

.vs/slnx.sqlite

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 16
+VisualStudioVersion = 16.0.29009.5
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "leetcode136", "leetcode136\leetcode136.csproj", "{D786D2BA-1A65-4CB6-821F-591C532DEC2C}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{D786D2BA-1A65-4CB6-821F-591C532DEC2C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D786D2BA-1A65-4CB6-821F-591C532DEC2C}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D786D2BA-1A65-4CB6-821F-591C532DEC2C}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D786D2BA-1A65-4CB6-821F-591C532DEC2C}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {88C08D01-35CE-4D2F-894D-0F2BE26AFE0E}
+	EndGlobalSection
+EndGlobal

leetcode136/.vs/leetcode136/DesignTimeBuild/.dtbcache

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+using System.Collections.Generic;
+using System.Linq;
+
+namespace leetcoce136a
+{
+    public class Solution
+    {
+        public int SingleNumber(int[] nums)
+        {
+            int res = 0;
+            Dictionary<int, int> dict = new Dictionary<int, int>();
+            foreach (var num in nums)
+            {
+                if (!dict.ContainsKey(num))
+                {
+                    dict.Add(num, 1);
+                }
+                else
+                    dict[num]++;
+            }
+
+            res = dict.FirstOrDefault(kv => kv.Value == 1).Key;
+
+            return res;
+        }
+
+        public static void Main()
+        {
+            var sol = new Solution();
+            int[] input = { 4, 1, 2, 1, 2 };
+
+            System.Console.WriteLine(sol.SingleNumber(input));
+        }
+    }
+}

leetcode136/.vs/leetcode136/v16/.suo

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+{
+  "runtimeTarget": {
+    "name": ".NETCoreApp,Version=v3.0",
+    "signature": ""
+  },
+  "compilationOptions": {},
+  "targets": {
+    ".NETCoreApp,Version=v3.0": {
+      "leetcode136/1.0.0": {
+        "dependencies": {
+          "runtime.win-x64.Microsoft.NETCore.DotNetAppHost": "3.0.0-preview5-27617-04"
+        },
+        "runtime": {
+          "leetcode136.dll": {}
+        }
+      },
+      "runtime.win-x64.Microsoft.NETCore.DotNetAppHost/3.0.0-preview5-27617-04": {}
+    }
+  },
+  "libraries": {
+    "leetcode136/1.0.0": {
+      "type": "project",
+      "serviceable": false,
+      "sha512": ""
+    },
+    "runtime.win-x64.Microsoft.NETCore.DotNetAppHost/3.0.0-preview5-27617-04": {
+      "type": "package",
+      "serviceable": true,
+      "sha512": "sha512-x+Vg5f2FW62/TbvlN++sDmnw+rS8q0TtnTRTn0JidDqwg3fwu6F9WXn9WgtXWGINV1OO8a7UVIioMTpnwbzBOQ==",
+      "path": "runtime.win-x64.microsoft.netcore.dotnetapphost/3.0.0-preview5-27617-04",
+      "hashPath": "runtime.win-x64.microsoft.netcore.dotnetapphost.3.0.0-preview5-27617-04.nupkg.sha512"
+    }
+  }
+}