How can you remove duplicate characters in a string?

Question

I have to implements a function that takes a string as an input and finds the non-duplicate character from this string.

So an an example is if I pass string str = \"

Answer 1

String str="AABBCANCDE";  
String newStr=""; 
for( int i=0; i<str.length(); i++)
{
 if(!newStr.contains(str.charAt(i)+""))
 newStr= newStr+str.charAt(i);
 }
 System.out.println(newStr);

Answer 2

char* removeDups(const char* str)
{
 char* new_str = (char*)malloc(256*sizeof(char));
 int i,j,current_pos = 0,len_of_new_str;
 new_str[0]='\0';

 for(i=0;i<strlen(str);i++)
{
 len_of_new_str = strlen(new_str);
for(j=0;j<len_of_new_str && new_str[j]!=str[i];j++)
   ;
  if(j==len_of_new_str)
   {
     new_str[len_of_new_str] = str[i];
     new_str[len_of_new_str+1] = '\0';
   }
}
  return new_str;
}

Hope this helps

Answer 3

Console.WriteLine("Enter String");

string str = Console.ReadLine();

string result = "";
result += str[0]; // first character of string

for (int i = 1; i < str.Length; i++)
{
    if (str[i - 1] != str[i])
        result += str[i];
}

Console.WriteLine(result);

Answer 4

//this is in C#, validation left out for brevity //primitive solution for removing duplicate chars from a given string

    public static char[] RemoveDup(string s)
    {
        char[] c = new char[s.Length];
        int unique = 0;
        c[unique] = s[0];  // Assume: First char is trivial
        for (int i = 1; i < s.Length; i++)
        {
            if (s[i-1] != s[i]
        c[++unique] = s[i];
        }
        return c;
    }

Answer 5

I like Quintin Robinson answer, only there should be some improvements like removing List, because it is not necessarry in this case. Also, in my opinion Uppercase char ("K") and lowercase char ("k") is the same thing, so they should be counted as one.

So here is how I would do it:

private static string RemoveDuplicates(string textEntered)
    {

        string newString = string.Empty;

        foreach (var c in textEntered)
        {
            if (newString.Contains(char.ToLower(c)) || newString.Contains(char.ToUpper(c)))
            {
                continue;
            }
            newString += c.ToString();
        }
        return newString;
    }

Answer 6

you may use HashSet:

 static void Main()
    {
        string textWithDuplicates = "aaabbcccggg";

        Console.WriteLine(textWithDuplicates.Count());  
        var letters = new HashSet<char>(textWithDuplicates);
        Console.WriteLine(letters.Count());

        foreach (char c in letters) Console.Write(c);   
    }