'How to create char array of letters from a string array ? (C#)

For example, I have a string:

"Nice to meet you"

, there are 13 letters when we count repeating letters, but I wanna create a char array of letters from this string without repeating letters, I mean for the string above it should create an array like

{'N', 'i', 'c', 'e', 't', 'o', 'y', 'u', 'm'}

I was looking for answers on google for 2 hours, but I found nothing, there were lots of answers about strings and char arrays, but were not answers for my situation. I thought that I can write code by checking every letter in the array by 2 for cycles but this time I got syntax errors, so I decided to ask.

c++sharparraysstringchar


Solution 1:[1]

You can do this:

var foo = "Nice to meet you";
var fooArr = s.ToCharArray();
HashSet<char> set = new();
set.UnionWith(fooArr);

//or if you want without whitespaces you could refactor this as below
set.UnionWith(fooArr.Where(c => c != ' '));

UPDATE: You could even make an extension method:

public static IEnumerable<char> ToUniqueCharArray(this string source, char? ignoreChar)
{
     var charArray = source.ToCharArray();
     HashSet<char> set = new();
     set.UnionWith(charArray.Where(c => c != ignoreChar));
     return set;
}

And then you can use it as:

var foo = "Nice to meet you";
var uniqueChars = foo.ToUniqueCharArray(ignoreChar: ' ');

// if you want to keep the whitespace
var uniqueChars = foo.ToUniqueCharArray(ignoreChar: null);

Solution 2:[2]

I tried this one and it works too

"Nice to meet you".Replace(" ", "").ToCharArray().Distinct();

Solution 3:[3]

A very short solution is to use .Except() on the input string:

string text = "Nice to meet you";

char[] letters = text.Except(" ").ToArray();

Here, .Except():

  1. translates both the text string and the parameter string (" ") to char collections
  2. filters out all the chars in the text char collection that are present in the parameter char collection
  3. returns a collection of distinct chars from the filtered text char collection

Example fiddle here.

Visualizing the process

Let's use the blue banana as an example.

var input = "blue banana";
  1. input.Except(" ") will be translated to:
{ 'b', 'l', 'u', 'e', ' ', 'b', 'a', 'n', 'a', 'n', 'a' }.Except({ ' ' })
  1. Filtering out all ' ' occurrences in the text char array produces:
{ 'b', 'l', 'u', 'e', 'b', 'a', 'n', 'a', 'n', 'a' }
  1. The distinct char collection will have all the duplicates of 'b', 'a' and 'n' removed, resulting in:
{ 'b', 'l', 'u', 'e', 'a', 'n' }

Solution 4:[4]

this piece of code does the job:

var sentence = "Nice To meet you";
var arr = sentence.ToLower().Where(x => x !=' ' ).ToHashSet();
Console.WriteLine(string.Join(",", arr));

I have added ToLower() if you dont do differences between uppercase and lowercase, if case is sensitive you just put off this extension.. HashSet suppresses all duplicates letters

test: Fiddle

Solution 5:[5]

ToCharArray method of string is only thing you need.

using System;

public class HelloWorld
{
     public static void Main(string[] args)
    {
        string str = "Nice to meet you"; 
        char[] carr = str.ToCharArray(); 
        for(int i = 0; i < carr.Length; i++)
            Console.WriteLine (carr[i]);
     }
}

Solution 6:[6]

String str  = "Nice To meet you";
char[] letters = str.ToLower().Except(" ").ToArray();

Solution 7:[7]

A solution just using for-loops (no generics or Linq), with comments explaining things:

// get rid of the spaces
String str = "Nice to meet you".Replace(" ", "");

// a temporary array more than long enough (we will trim it later)
char[] temp = new char[str.Length];

// the index where to insert the next char into "temp". This is also the length of the filled-in part
var idx = 0;

// loop through the source string
for (int i=0; i<str.Length; i++)
{
    // get the character at this position (NB "surrogate pairs" will fail here)
    var c = str[i];
    
    // did we find it in the following loop?
    var found = false;

    // loop through the collected characters to see if we already have it
    for (int j=0; j<idx; j++)
    {
        if (temp[j] == c)
        {
            // yes, we already have it!
            found = true;
            break;
        }
    }
    
    if (!found)
    {
        // we didn't already have it, so add
        temp[idx] = c;
        idx+=1;
    }
}

// "temp" is too long, so create a new array of the correct size
var letters = new char[idx];
Array.Copy(temp, letters, idx);
// now "letters" contains the unique letters

That "surrogate pairs" remark basically means that emojis will fail.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1
Solution 2
Solution 3 Astrid E.
Solution 4
Solution 5 Ugur Kasif Yuksel
Solution 6 Peter Csala
Solution 7 Hans Kesting

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