c# logic to get the first non-repeating(distinct) character from the string

Question

In c# i want to create logic that if i a string like abcabda is passed to a method then it should return first non repeative character from string like in above it should return c. i am unable to convert a string to array of character then how to make comparison of each array character to the string and return the first non repeative character.

please provide me some logic

can i make it like this

class A
{
    static void main()
    {
        A a=new A();
        char  ch=a.m1(abcabd);
    }
}

class B
{
    char m1(string s)
    {
        string s1=s;
        char[] ch1=new char[s.length];
        for(int x=0; x<s.length;x++)
        {
            ch1[x]=s[x];
        }
        for(int x=0; x<s.length; x++)
        {
            for(int y=0; y<s.lenth; y++)
            {
                if(s[x]=ch1[y])
                {             
/// here i am confused how to create logic for comparison please let me know
// and how to return the character
                }
            }
        }
    }
}

Answer 1

To read each character in a string is as simple as:

foreach (Char character in myString)
{

}

Answer 2

how about using LINQ?

string test = "abcabda";

var selectedChars = (from c in test.ToCharArray() 
                    group c by c into groups
                    where groups.Count() == 1
                    select groups).First();

This will return 'c' as per the example given in the question.

Answer 3

"string".ToCharArray() would give you an array containing characters that make "string"

Answer 4

I think you need to loop twice through the list of characters:

1. Once to build a Dictionary<char, int> of character-counts,
2. Then to find the first character in the string whose count equals 1

Answer 5

one possible solution: take each character from the string from right to left. for each char, check for any other occurence of the character in the string. if there is no other occurence of the char in the string, add it to a stack. once you have done this to all the chars in the string, the top of the stack would contain the first non-repetitive character.

Answer 6

It seems that you are looking for the first char in the string with its count equals to 1?

using System.Linq;
string str = "abcabda";
char result = str.FirstOrDefault(ch => str.IndexOf(ch) == str.LastIndexOf(ch));

Non LINQ version:

    for (int index = 0; index < str.Length; index++)
    {
        if (str.LastIndexOf(str[index]) == index)
        {
            result = str[index];
            break;
        }
    }

Answer 7

Pretty simple but:

    private char? findNonRepeat(string search)
    {
        foreach(char chr in search)
        {
            if (search.LastIndexOf(chr) == search.IndexOf(chr))
                return chr;
        }

        return null;
    }

Answer 8

You could use a bit of LINQ:

char result = input
    .GroupBy(c => c)             // group the characters
    .Where(g => g.Count() == 1)  // filter out groups with only 1 occurence
    .Select(g => g.Key)          // get the character from each remaining group
    .First();                    // return the first one

Answer 9

This may not be the most efficient, but it works and is easy to read:

    public string FirstNonRepeatingChar(string inString)
    {
        var array = inString.ToCharArray();
        foreach (char distinctChar in array.Distinct())
        {
            if (array.Count(x => x == distinctChar) == 1)
                return distinctChar.ToString();
        }
        return null; //none
    }

Answer 10

Here's your code so far:

char m1(string s) 
{ 
    string s1=s; 
    char[] ch1=new char[s.length]; 
    for(int x=0; x<s.length;x++) 
    { 
        ch1[x]=s[x]; 
    } 
    for(int x=0; x<s.length; x++) 
    { 
        for(int y=0; y<s.lenth; y++) 
        { 
            if(s[x]=ch1[y]) 
            {              
/// here i am confused how to create logic for comparison please let me know 
// and how to return the character 
            } 
        } 
    } 
} 

You're actually pretty close. I'm going to ignore all the stylistic problems and redundancies because they're not what you're asking about.

What you really want to do is step through your string character-by-character and see if that character exists later on in the string. If the character repeats, you can stop looking for it and go on to the next one. If you get to the end of the string without finding a repeat, you have found a non-duplicate character and can return it. You have most of the logic in your nested x/y loops, but are missing a few things:

    for(int x=0; x<s.length; x++) 
    {
        // you need a flag here to indicate whether your character is a duplicate
        for(int y=0; y<s.lenth; y++) // this loop should start at x+1, not 0
        { 
            if(s[x]=ch1[y]) // you need == instead of =
            {              
                // if you've gotten here, you have a duplicate --
                // set your flag to true and break out of the loop
            }
        }
        // at this point you should check your flag and
        // if it's not set, return your character: s[x]
    }

EDIT: You mentioned that you want to be able to find the string's length without calling Length, and presumably without naming any other methods. The way to do this is to use a foreach loop to iterate over the characters in the string, incrementing a counter as you go. Here is some code with comments for you to fill in:

// initialize counter to 0
foreach (char ch in s)
{
    // increment counter by 1
}
// now counter is the length of the string