Improve the solution. LeetCode #2109 'Adding Spaces to a String' [Med…

…ium].

LeetCode/src/LeetCode.Challenges/Problems21xx/N_2109_AddingSpacesToString/ImprovedSolution.cs

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+using System.Text;
+
+namespace LeetCode.Challenges.Problems21xx.N_2109_AddingSpacesToString;
+
+public static class ImprovedSolution
+{
+    public static string AddSpaces(string input, int[] spaces)
+    {
+        var sb = new StringBuilder();
+        var charPointer = 0;
+        var spacePointer = 0;
+
+        while (charPointer < input.Length)
+        {
+            if (spacePointer < spaces.Length && charPointer == spaces[spacePointer])
+            {
+                sb.Append(' ');
+                spacePointer++;
+            }
+
+            sb.Append(input[charPointer]);
+            charPointer++;
+        }
+
+        return sb.ToString();
+    }
+}

LeetCode/tests/LeetCode.Challenges.UnitTests/Problems21xx/N_2109_AddingSpacesToString/ImprovedSolutionTests.cs

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+using LeetCode.Challenges.Problems21xx.N_2109_AddingSpacesToString;
+using Shouldly;
+using Xunit;
+
+namespace LeetCode.Challenges.UnitTests.Problems21xx.N_2109_AddingSpacesToString;
+
+public class ImprovedSolutionTests
+{
+    [Theory]
+    [ClassData(typeof(TestData))]
+    public void GivenStringAndSpaces_WhenMinCapability_ThenResultAsExpected(
+        string input, int[] spaces, string expectedResult)
+    {
+        ImprovedSolution.AddSpaces(input, spaces).ShouldBeEquivalentTo(expectedResult);
+    }
+}