[#0165]feat(leetcode): Init project, add C# solution, unit test and README

problems/0165-compare-version-numbers/csharp/Program.cs

@@ -0,0 +1,144 @@
+// LeetCode 165: Compare Version Numbers
+// 難度: Medium
+// 日期: 2025-09-23
+
+using System;
+
+public class Solution
+{
+    // Two-pointer parser that compares segments without allocating intermediate arrays.
+    public int CompareVersion(string version1, string version2)
+    {
+        var i = 0;
+        var j = 0;
+
+        while (i < version1.Length || j < version2.Length)
+        {
+            var segment1 = NextSegment(version1, ref i);
+            var segment2 = NextSegment(version2, ref j);
+
+            var comparison = CompareSegments(segment1, segment2);
+            if (comparison != 0)
+            {
+                return comparison;
+            }
+        }
+
+        return 0;
+    }
+
+    // Reads the next numeric segment (between dots) as a span and advances the current index.
+    private static ReadOnlySpan<char> NextSegment(string version, ref int index)
+    {
+        if (index >= version.Length)
+        {
+            return ReadOnlySpan<char>.Empty;
+        }
+
+        var start = index;
+        while (index < version.Length && version[index] != '.')
+        {
+            index++;
+        }
+
+        var segment = version.AsSpan(start, index - start);
+
+        if (index < version.Length && version[index] == '.')
+        {
+            index++;
+        }
+
+        return segment;
+    }
+
+    // Compares two trimmed segments lexicographically to avoid integer overflow.
+    private static int CompareSegments(ReadOnlySpan<char> left, ReadOnlySpan<char> right)
+    {
+        left = TrimLeadingZeros(left);
+        right = TrimLeadingZeros(right);
+
+        if (left.Length > right.Length)
+        {
+            return 1;
+        }
+
+        if (left.Length < right.Length)
+        {
+            return -1;
+        }
+
+        for (var i = 0; i < left.Length; i++)
+        {
+            if (left[i] > right[i])
+            {
+                return 1;
+            }
+
+            if (left[i] < right[i])
+            {
+                return -1;
+            }
+        }
+
+        return 0;
+    }
+
+    private static ReadOnlySpan<char> TrimLeadingZeros(ReadOnlySpan<char> segment)
+    {
+        var index = 0;
+        while (index < segment.Length && segment[index] == '0')
+        {
+            index++;
+        }
+
+        return index == segment.Length ? ReadOnlySpan<char>.Empty : segment[index..];
+    }
+
+    public int MyCompareVersion(string version1, string version2)
+    {
+        var v1 = version1.Split('.');
+        var v2 = version2.Split('.');
+
+        if (v1.Length >= v2.Length)
+        {
+            return CompareString(v1, v2);
+        }
+
+        return CompareString(v2, v1) * -1;
+    }
+
+    private static int CompareString(string[] longer, string[] shorter)
+    {
+        for (var i = 0; i < longer.Length; i++)
+        {
+            _ = int.TryParse(longer[i], out var num1);
+            var num2 = i < shorter.Length && int.TryParse(shorter[i], out var parsed) ? parsed : 0;
+
+            if (num1 > num2)
+            {
+                return 1;
+            }
+
+            if (num1 < num2)
+            {
+                return -1;
+            }
+        }
+
+        return 0;
+    }
+}
+
+public class Program
+{
+    public static void Main(string[] args)
+    {
+        // optional: keep console app functional for manual verification
+        if (args.Length == 2)
+        {
+            var solution = new Solution();
+            var result = solution.CompareVersion(args[0], args[1]);
+            Console.WriteLine(result);
+        }
+    }
+}

problems/0165-compare-version-numbers/csharp/csharp.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+</Project>
+