How to remove duplicate characters in a string?

Question

I need to implement a function that takes a string as input and finds a non-double character from this string.

So, an example: if I pass the string str = "DHCD", it will return "DHC" or str2 = "KLKLHHMO" it will return "KLHMO"

Answer 1

Linq approach:

public static string RemoveDuplicates(string input) { return new string(input.ToCharArray().Distinct().ToArray()); } 

Answer 2

He will do the work

 string removedupes(string s) { string newString = string.Empty; List<char> found = new List<char>(); foreach(char c in s) { if(found.Contains(c)) continue; newString+=c.ToString(); found.Add(c); } return newString; } 

I must note that this is criminally ineffective.

I think I was delirious in the first revision.

Answer 3

For arbitrary character string lengths of byte size (not for wide characters or other encodings) I would use a lookup table, one bit per character (32 bytes for a 256-bit table). Scroll the line, only output characters that do not have their own bits, then turn on the bit for that character.

 string removedupes(string s) { string t; byte[] found = new byte[256]; foreach(char c in s) { if(!found[c]) { t.Append(c); found[c]=1; } } return t; } 

I am poorly versed in C #, so I don’t know how to use a bit field instead of an array of bytes.

If you know that your lines will be very short, then other approaches will make better use of memory and / or speed.

Answer 4

  void removeDuplicate() { string value1 = RemoveDuplicateChars("Devarajan"); } static string RemoveDuplicateChars(string key) { string result = ""; foreach (char value in key) if (result.IndexOf(value) == -1) result += value; return result; } 

Answer 5

It sounds like homework to me, so I’ll just describe it at a high level.

• Scroll through the line, exploring each character
• Check if you saw the character before
  • if you have, remove it from the line
  • If you haven’t done so, please note that you have already seen this symbol.

Answer 6

My answer is in Java.
Held here so you can get an idea, even if it is in Java. The algorithm will remain the same.

 public String removeDup(String s) { if(s==null) return null; int l = s.length(); //if length is less than 2 return string if(l<2)return s; char arr[] = s.toCharArray(); for(int i=0;i<l;i++) { int j =i+1; //index to check with ith index int t = i+1; //index of first repetative char. while(j<l) { if(arr[j]==arr[i]) { j++; } else { arr[t]=arr[j]; t++; j++; } } l=t; } return new String(arr,0,l); } 

Answer 7

// this is in C #, validation is left for brevity // a primitive solution to remove duplicate characters 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 8

you can 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); } 

Answer 9

char * remove_duplicates (char * str) {char * str1, * str2;

 if(!str) return str; str1 = str2 = str; while(*str2) { if(strchr(str, *str2)<str2) { str2++; continue; } *str1++ = *str2++; } *str1 = '\0'; return str; 

}

Answer 10

 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 11

 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 12

// Remove Both Upper Bottom Duplicates

 public static string RemoveDuplicates(string key) { string Result = string.Empty; foreach (char a in key) { if (Result.Contains(a.ToString().ToUpper()) || Result.Contains(a.ToString().ToLower())) continue; Result += a.ToString(); } return Result; } 

Answer 13

  class Program { static void Main(string[] args) { bool[] doesExists = new bool[256]; String st = Console.ReadLine(); StringBuilder sb = new StringBuilder(); foreach (char ch in st) { if (!doesExists[ch]) { sb.Append(ch); doesExists[ch] = true; } } Console.WriteLine(sb.ToString()); } } 

Answer 14

 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 15

I like Quintin Robinson's answer, only there should be some improvements, such as deleting the list, because in this case it is not necessary. In addition, in my opinion, the Uppercase char ("K") and the lowercase char ("k") are the same thing, so they should be considered the same.

So here is how I 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 16

Not sure how optimal this is:

 public static string RemoveDuplicates(string input) { var output = string.Join("", input.ToHashSet()); return output; } 

Answer 17

Below is the code to remove duplicate characters from a string

  var input = "SaaSingeshe"; var filteredString = new StringBuilder(); foreach(char c in input) { if(filteredString.ToString().IndexOf(c)==-1) { filteredString.Append(c); } } Console.WriteLine(filteredString); Console.ReadKey(); 

Answer 18

Demonstration of the namespace {class Program {

  static void Main(string[] args) { string myStr = "kkllmmnnouo"; Console.WriteLine("Initial String: "+myStr); // var unique = new HashSet<char>(myStr); HashSet<char> unique = new HashSet<char>(myStr); Console.Write("New String after removing duplicates: "); foreach (char c in unique) Console.Write(c); } } } 

Answer 19

revised version of first answer in C # below

string oldstr = "abacab";

string newstr = new string (oldstr.Distinct (). ToArray ());

Answer 20

 var input1 = Console.ReadLine().ToLower().ToCharArray(); var input2 = input1; var WithoutDuplicate = input1.Union(input2);