Remove extra spaces from a string

// C# program to implement custom trim() function
using System;

public class Gfg
{
    public static void Main()
    {
        string str = "   Hello Geeks . Welcome   to" +
                     "  GeeksforGeeks   .    ";

        removeSpaces(ref str);

        Console.WriteLine(str);
    }

    // Function to in-place trim all spaces in the
    // string such that all words should contain only
    // a single space between them.
    public static void removeSpaces(ref string str)
    {
        // n is length of the original string
        int n = str.Length;

        // i points to next position to be filled in
        // output string/ j points to next character
        // in the original string
        int i = 0, j = -1;

        // flag that sets to true is space is found
        bool spaceFound = false;

        // Handles leading spaces
        while (++j < n && str[j] == ' ');

        // read all characters of original string
        while (j < n)
        {
            // if current characters is non-space
            if (str[j] != ' ')
            {
                // remove preceding spaces before dot,
                // comma & question mark
                if ((str[j] == '.' || str[j] == ',' ||
                     str[j] == '?') && i - 1 >= 0 &&
                     str[i - 1] == ' ')
                    str = str.Remove(i - 1, 1).Insert(i - 1, str[j++].ToString());
                else
                {
                    // copy current character at index i
                    // and increment both i and j
                    str = str.Remove(i, 1).Insert(i, str[j++].ToString());
                    i++;
                }

                // set space flag to false when any
                // non-space character is found
                spaceFound = false;
            }
            // if current character is a space
            else if (str[j++] == ' ')
            {
                // If space is encountered for the first
                // time after a word, put one space in the
                // output and set space flag to true
                if (!spaceFound)
                {
                    str = str.Remove(i, 0).Insert(i, " ");
                    i++;
                    spaceFound = true;
                }
            }
        }

        // Remove trailing spaces
        if (i <= 1)
            str = str.Remove(i, n - i);
        else
            str = str.Remove(i - 1, n - i + 1);
    }
}

using System;

class Program
{
    static void Main()
    {
        string inputString = "   Hello Geeks  .  Welcome to GeeksforGeeks ,    Do you love Geeks , Geeks  ? ";
        char[] outputArray = new char[inputString.Length]; // Using char array for efficient string building
        int outputIndex = 0;
        bool spaceFlag = false; // Flag to check if spaces have occurred

        for (int index = 0; index < inputString.Length; ++index)
        {
            if (inputString[index] != ' ')
            {
                if (spaceFlag)
                {
                    // Check if the current character is a punctuation mark
                    if (inputString[index] == '.' || inputString[index] == '?' || inputString[index] == ',')
                    {
                        // Do nothing
                    }
                    else
                    {
                        outputArray[outputIndex++] = ' ';
                    }
                    spaceFlag = false;
                }
                outputArray[outputIndex++] = inputString[index];
            }
            else if (index > 0 && inputString[index - 1] != ' ')
            {
                spaceFlag = true;
            }
        }

        string outputString = new string(outputArray, 0, outputIndex); // Convert char array to string

        Console.WriteLine(outputString);
    }
}

// C# Program to remove
// extra spaces from a string
using System;

class Program {
    static void Main(string[] args)
    {
        string str
            = "   Hello Geeks  .  Welcome ,    Do you love Geeks , Geeks  ? ";
        // Removing extra spaces using regex and print
        Console.WriteLine(
            System.Text.RegularExpressions.Regex.Replace(
                str.Trim(), @"\s+", " "));
    }
}