using System.Collections.Generic;
public static string ModifyString(string inputStr,
if (string.IsNullOrEmpty(inputStr))
var copyString = new StringBuilder(inputStr);
for (int i = 0; i < copyString.Length - 1; i++)
if (delimiters.Contains(copyString[i]) &&
!delimiters.Contains(copyString[i + 1]))
if (index == replaceIndex)
return copyString.ToString();
public static void Main()
Console.WriteLine("UniLecs");
var delimiters = new List<char>() { ' ', ',', '.', '?', '!' };
string inputString = "Lorem ipsum dolor sit amet, consectetur adipiscing elit.";
Console.WriteLine(ModifyString(inputString, 2, '%', delimiters));