Skip to main content

program to find first non repeating character in a string c# - 3 ways

In c# you want to create logic that if a string like "abcabd" is passed to a method then it should return first non repetitive character from string like in above it should return "c".

Below is three way to get the first non-repeating(distinct) character from the string -
  • First using IndexOf and LastIndexOf method of string type.
  • Using for loop and comparing operator.
  • Using Linq GroupBy method.
If we are talking about performance ( like execution time, complexity etc ) and arranging the above three ways in ascending order of execution time then sequence must be as below -

Using for loop and comparing operator >> using IndexOf and LastIndexOf method of string type >> Using Linq GroupBy method.

Find the first non-repeated character in a string - IndexOf Method


public char firstNonRepetitive(string inputString)
{
    char firstDistinctChar = ' ';
    for (int i = 0; i < inputString.Length; i++)
    {
        if (inputString.IndexOf(inputString[i], i + 1) == -1)
        {
            firstDistinctChar = inputString[i];
            break;
        }
    }
    return firstDistinctChar;

}

IndexOf and LastIndexOf method with nallable char type  


//nullable char type
public char? firstNonRepetitive(string inputString)
{
    for (int i = 0; i < inputString.Length; i++)
    {
        if (inputString.IndexOf(inputString[i]) == inputString.LastIndexOf(inputString[i]))
            return inputString[i];
    }
    return null;

}


Get the first non-repeating(distinct) character from the string - for loop


public char firstNonRepetitive(string inputString)
{
    int nextOccurrence = 0;
    char firstDistinctChar = ' ';
    for (int i = 0; i < inputString.Length; i++)
    {
        nextOccurrence = 0;
        for (int j = (i + 1); j < inputString.Length; j++)
        {
            if (inputString[i] == inputString[j])
                nextOccurrence++;
        }
        if (nextOccurrence == 0)
        {
            firstDistinctChar = inputString[i];
            break;
        }
    }
    return firstDistinctChar;

}


Find First Non Repeated Character in String - LINQ - Code


public char firstNonRepetitive(string inputString)
{
   char firstDistinctChar = ' ';

   firstDistinctChar = inputString.GroupBy(x => x).Where(x => x.Count() == 1).Select(x => x.Key).First();

   return firstDistinctChar;
}



public char firstNonRepetitive(string inputString)
{
   char firstDistinctChar = ' ';

   firstDistinctChar = (from chr in inputString group chr by chr into charGroups where charGroups.Count() == 1 select charGroups.Key).First();

   return firstDistinctChar;
}


Input - "abcabd"


string duplicateCharString = "abcabd";
firstNonRepetitive(duplicateCharString);

Output - "c"


Popular posts from this blog

Merging multiple PDFs using iTextSharp in asp.net c#

In this article i will show you how to merge multiple pdfs into one using ITextSharp below is the two approach one is to pass your input files path, output file path (will be created if not exist) and another is pass direct input stream, output stream and it will write the merge files into output stream.

how $document.ready() is different from window.onload()

we often use window.onload() in javascript and $document.ready() in jquery and assume that both are same just jquery library wrap up javascript window.onload() and introduce $document.ready() but no there is much difference between them below is the explanation -

Uploading large file in chunks in Asp.net Mvc c# from Javascript ajax

Often we have a requirement to upload files in Asp.net, Mvc c# application but when it comes to uploading larger file, we always think how to do it as uploading large file in one go have many challenges like UI responsiveness, If network fluctuate for a moment in between then uploading task get breaks and user have to upload it again etc.

Scrollable Gridview with fixed headers in asp.net

horizontal and vertical scrollable Gridview with static header row.fixed header in gridview in asp.net.static header in gridview through java script.I was looking for a solution for this for a long time and found most of the answers are not working or not suitable for my situation i also find most of the java script code for that they worked but only with the vertical scroll not with the horizontal scroll and also combination of header and rows doesn't match.

How to handle click event of linkbutton inside gridview

Recently I have posted how to sort only current page of gridview, Scrollble gridview with fixed header through javascript, File upload control inside gridview during postback and now i am going to explain how to handle click event of linkbutton or any button type control inside gridview.

We can handle click event of any button type control inside gridview by two way first is through event bubbling and second one is directly (in this type of event handling we need to access current girdviewrow container)