[#3446] feat(SortMatrix): add C# solution

202508/3446 SortMatrix/C#/C#.sln

@@ -0,0 +1,24 @@
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.5.2.0
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SortMatrix", "SortMatrix.csproj", "{60318F94-4F41-A4B8-C189-A8135ECCECCB}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{60318F94-4F41-A4B8-C189-A8135ECCECCB}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{60318F94-4F41-A4B8-C189-A8135ECCECCB}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{60318F94-4F41-A4B8-C189-A8135ECCECCB}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{60318F94-4F41-A4B8-C189-A8135ECCECCB}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {9F59D1F6-D9F3-492C-BC39-A5771AF22B36}
+	EndGlobalSection
+EndGlobal

202508/3446 SortMatrix/C#/Program.cs

@@ -0,0 +1,115 @@
+public class Solution
+{
+    public int[][] SortMatrix(int[][] grid)
+    {
+        // 左下
+        var leftDiagonals = new Dictionary<int, List<int>>();
+        for (var i = 0; i < grid.Length; i++)
+        {
+            // total -> 2n + 1 way
+            for (var j = 0; j <= i; j++)
+            {
+                int diagonal = i - j;
+                if (!leftDiagonals.ContainsKey(diagonal))
+                {
+                    leftDiagonals[diagonal] = new List<int>();
+                }
+                leftDiagonals[diagonal].Add(grid[i][j]);
+            }
+        }
+
+        // 右上
+        var rightDiagonals = new Dictionary<int, List<int>>();
+        for (var i = 0; i < grid.Length; i++)
+        {
+            for (var j = i; j < grid.Length; j++)
+            {
+                int diagonal = j - i;
+                if (!rightDiagonals.ContainsKey(diagonal))
+                {
+                    rightDiagonals[diagonal] = new List<int>();
+                }
+                rightDiagonals[diagonal].Add(grid[i][j]);
+            }
+        }
+
+        foreach (var diagonal in leftDiagonals.Values)
+        {
+            diagonal.Sort((a, b) => b.CompareTo(a));
+        }
+
+        foreach (var diagonal in rightDiagonals.Values)
+        {
+            diagonal.Sort((a, b) => a.CompareTo(b));
+        }
+
+        for (var i = 0; i < grid.Length; i++)
+        {
+            for (var j = 0; j <= i; j++)
+            {
+                int diagonal = i - j;
+                grid[i][j] = leftDiagonals[diagonal][0];
+                leftDiagonals[diagonal].RemoveAt(0);
+            }
+
+            for (var j = i; j < grid.Length; j++)
+            {
+                if (i == j) continue;
+                int diagonal = j - i;
+                grid[i][j] = rightDiagonals[diagonal][0];
+                rightDiagonals[diagonal].RemoveAt(0);
+            }
+        }
+        return grid;
+    }
+}
+
+public class Solution2 {
+    public int[][] SortMatrix(int[][] grid) {
+        int n = grid.Length;
+
+        for (int i = 0; i < n; i++) {
+            List<int> tmp = new List<int>();
+            for (int j = 0; i + j < n; j++) {
+                tmp.Add(grid[i + j][j]);
+            }
+            tmp.Sort((a, b) => b.CompareTo(a));
+            for (int j = 0; i + j < n; j++) {
+                grid[i + j][j] = tmp[j];
+            }
+        }
+
+        for (int j = 1; j < n; j++) {
+            List<int> tmp = new List<int>();
+            for (int i = 0; j + i < n; i++) {
+                tmp.Add(grid[i][j + i]);
+            }
+            tmp.Sort();
+            for (int i = 0; j + i < n; i++) {
+                grid[i][j + i] = tmp[i];
+            }
+        }
+
+        return grid;
+    }
+}
+
+class Program
+{
+    static void Main()
+    {
+        var Solution = new Solution();
+
+        var gird = new int[][] { [1, 7, 3], [9, 8, 2], [4, 5, 6] };
+        var result = Solution.SortMatrix(gird);
+
+        for (int i = 0; i < result.Length; i++)
+        {
+            for (int j = 0; j < result[i].Length; j++)
+            {
+                Console.Write(result[i][j] + " ");
+            }
+            Console.WriteLine();
+        }
+    }
+}

202508/3446 SortMatrix/C#/SortMatrix.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>