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Determine if a string has all Unique Characters

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Given a string, determine if the string has all unique characters.

Examples :  

Input : abcd10jk
Output : true

Input : hutg9mnd!nk9
Output : false

Approach 1 – Brute Force technique: Run 2 loops with variable i and j. Compare str[i] and str[j]. If they become equal at any point, return false. 

C++




// C++ program to illustrate string
// with unique characters using
// brute force technique
#include <bits/stdc++.h>
using namespace std;
 
bool uniqueCharacters(string str)
{
 
    // If at any time we encounter 2
    // same characters, return false
    for (int i = 0; i < str.length() - 1; i++) {
        for (int j = i + 1; j < str.length(); j++) {
            if (str[i] == str[j]) {
                return false;
            }
        }
    }
 
    // If no duplicate characters encountered,
    // return true
    return true;
}
 
// driver code
int main()
{
    string str = "GeeksforGeeks";
 
    if (uniqueCharacters(str)) {
        cout << "The String " << str
             << " has all unique characters\n";
    }
    else {
        cout << "The String " << str
             << " has duplicate characters\n";
    }
    return 0;
}
// This code is contributed by Divyam Madaan


Java




// Java program to illustrate string with
// unique characters using brute force technique
import java.util.*;
 
class GfG {
    boolean uniqueCharacters(String str)
    {
        // If at any time we encounter 2 same
        // characters, return false
        for (int i = 0; i < str.length(); i++)
            for (int j = i + 1; j < str.length(); j++)
                if (str.charAt(i) == str.charAt(j))
                    return false;
 
        // If no duplicate characters encountered,
        // return true
        return true;
    }
 
    public static void main(String args[])
    {
        GfG obj = new GfG();
        String input = "GeeksforGeeks";
 
        if (obj.uniqueCharacters(input))
            System.out.println("The String " + input + " has all unique characters");
        else
            System.out.println("The String " + input + " has duplicate characters");
    }
}


Python3




# Python program to illustrate string
# with unique characters using
# brute force technique
 
def uniqueCharacters(str):
     
    # If at any time we encounter 2
    # same characters, return false
    for i in range(len(str)):
        for j in range(i + 1,len(str)):
            if(str[i] == str[j]):
                return False;
 
    # If no duplicate characters
    # encountered, return true
    return True;
 
 
# Driver Code
str = "GeeksforGeeks";
 
if(uniqueCharacters(str)):
    print("The String ", str," has all unique characters");
else:
    print("The String ", str, " has duplicate characters");
 
# This code contributed by PrinciRaj1992


C#




// C# program to illustrate string with
// unique characters using brute force
// technique
using System;
 
public class GFG {
 
    static bool uniqueCharacters(String str)
    {
 
        // If at any time we encounter 2
        // same characters, return false
        for (int i = 0; i < str.Length; i++)
            for (int j = i + 1; j < str.Length; j++)
                if (str[i] == str[j])
                    return false;
 
        // If no duplicate characters
        // encountered, return true
        return true;
    }
 
    public static void Main()
    {
        string input = "GeeksforGeeks";
 
        if (uniqueCharacters(input) == true)
            Console.WriteLine("The String " + input
                              + " has all unique characters");
        else
            Console.WriteLine("The String " + input
                              + " has duplicate characters");
    }
}
 
// This code is contributed by shiv_bhakt.


PHP




<?php
// PHP program to illustrate string
// with unique characters using
// brute force technique
 
function uniqueCharacters($str)
{
     
    // If at any time we encounter 2
    // same characters, return false
    for($i = 0; $i < strlen($str); $i++)
    {
        for($j = $i + 1; $j < strlen($str); $j++)
        {
            if($str[$i] == $str[$j])
            {
                return false;
            }
        }
    }
     
    // If no duplicate characters
    // encountered, return true
    return true;
}
 
// Driver Code
$str = "GeeksforGeeks";
 
if(uniqueCharacters($str))
{
    echo "The String ", $str,
          " has all unique characters\n";
}
else
{
    echo "The String ", $str,
         " has duplicate characters\n";
}
 
// This code is contributed by ajit
?>


Javascript




<script>
 
// Javascript program to illustrate string with
// unique characters using brute force
// technique
function uniqueCharacters(str)
{
     
    // If at any time we encounter 2
    // same characters, return false
    for(let i = 0; i < str.length; i++)
        for(let j = i + 1; j < str.length; j++)
            if (str[i] == str[j])
                return false;
 
    // If no duplicate characters
    // encountered, return true
    return true;
}
 
// Driver code
let input = "GeeksforGeeks";
 
if (uniqueCharacters(input) == true)
    document.write("The String " + input +
                   " has all unique characters" + "</br>");
else
    document.write("The String " + input +
                   " has duplicate characters");
                  
// This code is contributed by decode2207
 
</script>


Output : 

The String GeeksforGeeks has duplicate characters

Time Complexity: O(n2

Auxiliary Space: O(1)
Note: Please note that the program is case-sensitive.

Approach 2 – Sorting: Using sorting based on ASCII values of characters 

C++




// C++ program to illustrate string
// with unique characters using
// brute force technique
#include <bits/stdc++.h>
using namespace std;
 
bool uniqueCharacters(string str)
{
 
    // Using sorting
    sort(str.begin(), str.end());
 
    for (int i = 0; i < str.length()-1; i++) {
 
        // if at any time, 2 adjacent
        // elements become equal,
        // return false
        if (str[i] == str[i + 1]) {
            return false;
        }
    }
    return true;
}
 
// driver code
int main()
{
 
    string str = "GeeksforGeeks";
 
    if (uniqueCharacters(str)) {
        cout << "The String " << str
             << " has all unique characters\n";
    }
    else {
 
        cout << "The String " << str
             << " has duplicate characters\n";
    }
    return 0;
}
// This code is contributed by Divyam Madaan


Java




// Java program to check string with unique
// characters using sorting technique
import java.util.*;
 
class GfG {
    /* Convert the string to character array
       for sorting */
    boolean uniqueCharacters(String str)
    {
        char[] chArray = str.toCharArray();
 
        // Using sorting
        // Arrays.sort() uses binarySort in the background
        // for non-primitives which is of O(nlogn) time complexity
        Arrays.sort(chArray);
 
        for (int i = 0; i < chArray.length - 1; i++) {
            // if the adjacent elements are not
            // equal, move to next element
            if (chArray[i] != chArray[i + 1])
                continue;
 
            // if at any time, 2 adjacent elements
            // become equal, return false
            else
                return false;
        }
        return true;
    }
 
    // Driver code
    public static void main(String args[])
    {
        GfG obj = new GfG();
        String input = "GeeksforGeeks";
 
        if (obj.uniqueCharacters(input))
            System.out.println("The String " + input
                               + " has all unique characters");
        else
            System.out.println("The String " + input
                               + " has duplicate characters");
    }
}


Python3




# Python3 program to illustrate string
# with unique characters using
# brute force technique
def uniqueCharacters(st):
 
    # Using sorting
    st = sorted(st)
 
    for i in range(len(st)-1):
 
        # if at any time, 2 adjacent
        # elements become equal,
        # return false
        if (st[i] == st[i + 1]) :
            return False
             
    return True
 
# Driver code
if __name__=='__main__':
 
    st = "GeeksforGeeks"
 
    if (uniqueCharacters(st)) :
        print("The String",st,"has all unique characters\n")
     
    else :
        print("The String",st,"has duplicate characters\n")
     
 
# This code is contributed by AbhiThakur


C#




// C# program to check string with unique
// characters using sorting technique
using System;
 
public class GFG {
 
    /* Convert the string to character array
    for sorting */
    static bool uniqueCharacters(String str)
    {
        char[] chArray = str.ToCharArray();
 
        // Using sorting
        Array.Sort(chArray);
 
        for (int i = 0; i < chArray.Length - 1; i++) {
 
            // if the adjacent elements are not
            // equal, move to next element
            if (chArray[i] != chArray[i + 1])
                continue;
 
            // if at any time, 2 adjacent elements
            // become equal, return false
            else
                return false;
        }
 
        return true;
    }
 
    // Driver code
    public static void Main()
    {
        string input = "GeeksforGeeks";
 
        if (uniqueCharacters(input) == true)
            Console.WriteLine("The String " + input
                              + " has all unique characters");
        else
            Console.WriteLine("The String " + input
                              + " has duplicate characters");
    }
}
 
// This code is contributed by shiv_bhakt.


Javascript




<script>
 
    // Javascript program to
    // check string with unique
    // characters using sorting technique
     
    /* Convert the string to character array
    for sorting */
    function uniqueCharacters(str)
    {
        let chArray = str.split('');
  
        // Using sorting
        chArray.sort();
  
        for (let i = 0; i < chArray.length - 1; i++)
        {
  
            // if the adjacent elements are not
            // equal, move to next element
            if (chArray[i] != chArray[i + 1])
                continue;
  
            // if at any time, 2 adjacent elements
            // become equal, return false
            else
                return false;
        }
  
        return true;
    }
     
    let input = "GeeksforGeeks";
  
    if (uniqueCharacters(input) == true)
      document.write("The String " + input +
      " has all unique characters" + "</br>");
    else
      document.write("The String " + input +
      " has duplicate characters" + "</br>");
     
</script>


Output: 

The String GeeksforGeeks has duplicate characters

Time Complexity: O(nlogn)  

Auxiliary Space: O(1)

Approach 3 – Use of Extra Data Structure: This approach assumes ASCII char set(8 bits). The idea is to maintain a boolean array for the characters. The 256 indices represent 256 characters. All the array elements are initially set to false. As we iterate over the string, set true at the index equal to the int value of the character. If at any time, we encounter that the array value is already true, it means the character with that int value is repeated. 

C++




#include <cstring>
#include <iostream>
using namespace std;
 
const int MAX_CHAR = 256;
 
bool uniqueCharacters(string str)
{
 
    // If length is greater than 265,
    // some characters must have been repeated
    if (str.length() > MAX_CHAR)
        return false;
 
    bool chars[MAX_CHAR] = { 0 };
    for (int i = 0; i < str.length(); i++) {
        if (chars[int(str[i])] == true)
            return false;
 
        chars[int(str[i])] = true;
    }
    return true;
}
 
// driver code
int main()
{
    string str = "GeeksforGeeks";
 
    if (uniqueCharacters(str)) {
        cout << "The String " << str
             << " has all unique characters\n";
    }
    else {
 
        cout << "The String " << str
             << " has duplicate characters\n";
    }
    return 0;
}
// This code is contributed by Divyam Madaan


Java




// Java program to illustrate String With
// Unique Characters using data structure
import java.util.*;
 
class GfG {
    int MAX_CHAR = 256;
 
    boolean uniqueCharacters(String str)
    {
        // If length is greater than 256,
        // some characters must have been repeated
        if (str.length() > MAX_CHAR)
            return false;
 
        boolean[] chars = new boolean[MAX_CHAR];
        Arrays.fill(chars, false);
 
        for (int i = 0; i < str.length(); i++) {
            int index = (int)str.charAt(i);
 
            /* If the value is already true, string
               has duplicate characters, return false */
            if (chars[index] == true)
                return false;
 
            chars[index] = true;
        }
 
        /* No duplicates encountered, return true */
        return true;
    }
 
    // Driver code
    public static void main(String args[])
    {
        GfG obj = new GfG();
        String input = "GeeksforGeeks";
 
        if (obj.uniqueCharacters(input))
            System.out.println("The String " + input
                               + " has all unique characters");
        else
            System.out.println("The String " + input
                               + " has duplicate characters");
    }
}


Python3




# Python program to illustrate
# string with unique characters
# using data structure
MAX_CHAR = 256;
 
def uniqueCharacters(string):
    n = len(string)
     
    # If length is greater than 256,
    # some characters must have
    # been repeated
    if n > MAX_CHAR:
        return False
 
    chars = [False] * MAX_CHAR
 
    for i in range(n):
        index = ord(string[i])
 
        '''
         * If the value is already True,
         string has duplicate characters,
         return False'''
        if (chars[index] == True):
            return False
 
        chars[index] = True
 
    ''' No duplicates encountered,
        return True '''
    return True
 
# Driver code
if __name__ == '__main__':
   
    input = "GeeksforGeeks"
    if (uniqueCharacters(input)):
        print("The String", input,
              "has all unique characters")
    else:
        print("The String", input,
              "has duplicate characters")
 
# This code is contributed by shikhasingrajput


C#




// C# program to illustrate String With
// Unique Characters using data structure
using System;
 
class GfG {
    static int MAX_CHAR = 256;
 
    bool uniqueCharacters(String str)
    {
        // If length is greater than 256,
        // some characters must have been repeated
        if (str.Length > MAX_CHAR)
            return false;
 
        bool[] chars = new bool[MAX_CHAR];
        for (int i = 0; i < MAX_CHAR; i++) {
            chars[i] = false;
        }
        for (int i = 0; i < str.Length; i++) {
            int index = (int)str[i];
 
            /* If the value is already true, string
            has duplicate characters, return false */
            if (chars[index] == true)
                return false;
 
            chars[index] = true;
        }
 
        /* No duplicates encountered, return true */
        return true;
    }
 
    // Driver code
    public static void Main(String[] args)
    {
        GfG obj = new GfG();
        String input = "GeeksforGeeks";
 
        if (obj.uniqueCharacters(input))
            Console.WriteLine("The String " + input
                              + " has all unique characters");
        else
            Console.WriteLine("The String " + input
                              + " has duplicate characters");
    }
}
 
// This code has been contributed by 29AjayKumar


Javascript




<script>
    // Javascript program to illustrate String With
    // Unique Characters using data structure
     
    let MAX_CHAR = 256;
  
    function uniqueCharacters(str)
    {
        // If length is greater than 256,
        // some characters must have been repeated
        if (str.length > MAX_CHAR)
            return false;
  
        let chars = new Array(MAX_CHAR);
        for (let i = 0; i < MAX_CHAR; i++) {
            chars[i] = false;
        }
        for (let i = 0; i < str.length; i++) {
            let index = str[i].charCodeAt();
  
            /* If the value is already true, string
            has duplicate characters, return false */
            if (chars[index] == true)
                return false;
  
            chars[index] = true;
        }
  
        /* No duplicates encountered, return true */
        return true;
    }
     
    let input = "GeeksforGeeks";
 
    if (uniqueCharacters(input))
      document.write("The String " + input
                        + " has all unique characters");
    else
      document.write("The String " + input
                        + " has duplicate characters");
     
</script>


Output:

The String GeeksforGeeks has duplicate characters

Time Complexity: O(n) 

Auxiliary Space: O(n)

Approach 4 – Without Extra Data Structure: The approach is valid for strings having alphabet as a-z. This approach is a little tricky. Instead of maintaining a boolean array, we maintain an integer value called checker(32 bits). As we iterate over the string, we find the int value of the character with respect to ‘a’ with the statement int bitAtIndex = str.charAt(i)-‘a’; 
Then the bit at that int value is set to 1 with the statement 1 << bitAtIndex
Now, if this bit is already set in the checker, the bit AND operation would make the checker > 0. Return false in this case. 
Else Update checker to make the bit 1 at that index with the statement checker = checker | (1 <<bitAtIndex); 

C++




// C++ program to illustrate string
// with unique characters using
// brute force technique
#include <bits/stdc++.h>
using namespace std;
 
bool uniqueCharacters(string str)
{
 
    // Assuming string can have characters
    // a-z, this has 32 bits set to 0
    int checker = 0;
 
    for (int i = 0; i < str.length(); i++) {
 
        int bitAtIndex = str[i] - 'a';
 
        // if that bit is already set in
        // checker, return false
        if ((checker & (1 << bitAtIndex)) > 0) {
            return false;
        }
 
        // otherwise update and continue by
        // setting that bit in the checker
        checker = checker | (1 << bitAtIndex);
    }
 
    // no duplicates encountered, return true
    return true;
}
 
// driver code
int main()
{
 
    string str = "geeksforgeeks";
 
    if (uniqueCharacters(str)) {
        cout << "The String " << str
             << " has all unique characters\n";
    }
    else {
        cout << "The String " << str
             << " has duplicate characters\n";
    }
    return 0;
}
// This code is contributed by Divyam Madaan


Java




// Java program to illustrate String with unique
// characters without using any data structure
import java.util.*;
 
class GfG {
    boolean uniqueCharacters(String str)
    {
        // Assuming string can have characters a-z
        // this has 32 bits set to 0
        int checker = 0;
 
        for (int i = 0; i < str.length(); i++) {
            int bitAtIndex = str.charAt(i) - 'a';
 
            // if that bit is already set in checker,
            // return false
            if ((checker & (1 << bitAtIndex)) > 0)
                return false;
 
            // otherwise update and continue by
            // setting that bit in the checker
            checker = checker | (1 << bitAtIndex);
        }
 
        // no duplicates encountered, return true
        return true;
    }
 
    // Driver Code
    public static void main(String args[])
    {
        GfG obj = new GfG();
        String input = "geekforgeeks";
 
        if (obj.uniqueCharacters(input))
            System.out.println("The String " + input
                               + " has all unique characters");
        else
            System.out.println("The String " + input
                               + " has duplicate characters");
    }
}


Python3




# Python3 program to illustrate String with unique
# characters without using any data structure
import math
 
def uniqueCharacters(string):
     
    # Assuming string can have characters
    # a-z this has 32 bits set to 0
    checker = 0
     
    for i in range(len(string)):
        bitAtIndex = ord(string[i]) - ord('a')
 
        # If that bit is already set in
        # checker, return False
        if ((bitAtIndex) > 0):
            if ((checker & ((1 << bitAtIndex))) > 0):
                return False
                 
            # Otherwise update and continue by
            # setting that bit in the checker
            checker = checker | (1 << bitAtIndex)
 
    # No duplicates encountered, return True
    return True
 
# Driver Code
if __name__ == '__main__':
     
    input = "geekforgeeks"
 
    if (uniqueCharacters(input)):
        print("The String " + input +
              " has all unique characters")
    else:
        print("The String " + input +
              " has duplicate characters")
 
# This code is contributed by Princi Singh


C#




// C# program to illustrate String
// with unique characters without
// using any data structure
using System;
 
class GFG {
    public virtual bool uniqueCharacters(string str)
    {
        // Assuming string can have
        // characters a-z this has
        // 32 bits set to 0
        int checker = 0;
 
        for (int i = 0; i < str.Length; i++) {
            int bitAtIndex = str[i] - 'a';
 
            // if that bit is already set
            // in checker, return false
            if ((checker & (1 << bitAtIndex)) > 0) {
                return false;
            }
 
            // otherwise update and continue by
            // setting that bit in the checker
            checker = checker | (1 << bitAtIndex);
        }
 
        // no duplicates encountered,
        // return true
        return true;
    }
 
    // Driver Code
    public static void Main(string[] args)
    {
        GFG obj = new GFG();
        string input = "geekforgeeks";
 
        if (obj.uniqueCharacters(input)) {
            Console.WriteLine("The String " + input + " has all unique characters");
        }
        else {
            Console.WriteLine("The String " + input + " has duplicate characters");
        }
    }
}
 
// This code is contributed by Shrikant13


PHP




<?php
// PHP program to illustrate
// string with unique characters
// using brute force technique
function uniqueCharacters($str)
{
     
    // Assuming string can have
    // characters a-z, this has
    // 32 bits set to 0
    $checker = 0;
     
    for ($i = 0; $i < strlen($str); $i++)
    {
        $bitAtIndex = $str[$i] - 'a';
         
        // if that bit is already set
        // in checker, return false
        if (($checker &
            (1 << $bitAtIndex)) > 0)
        {
            return false;
        }
         
    // otherwise update and continue by
    // setting that bit in the checker
    $checker = $checker |
               (1 << $bitAtIndex);
    }
     
    // no duplicates encountered,
    // return true
    return true;
}
 
// Driver Code
$str = "geeksforgeeks";
 
if(uniqueCharacters($str))
{
    echo "The String ", $str,
         " has all unique characters\n";
}
else
{
    echo "The String ", $str,
         " has duplicate characters\n";
}
 
// This code is contributed by ajit
?>


Javascript




<script>
    // Javascript program to illustrate String
    // with unique characters without
    // using any data structure
     
    function uniqueCharacters(str)
    {
        // Assuming string can have
        // characters a-z this has
        // 32 bits set to 0
        let checker = 0;
  
        for (let i = 0; i < str.length; i++) {
            let bitAtIndex = str[i].charCodeAt(0) - 'a'.charCodeAt(0);
  
            // if that bit is already set
            // in checker, return false
            if ((checker & (1 << bitAtIndex)) > 0) {
                return false;
            }
  
            // otherwise update and continue by
            // setting that bit in the checker
            checker = checker | (1 << bitAtIndex);
        }
  
        // no duplicates encountered,
        // return true
        return true;
    }
     
    let input = "geekforgeeks";
  
    if (uniqueCharacters(input)) {
      document.write("The String " + input + " has all unique characters");
    }
    else {
      document.write("The String " + input + " has duplicate characters");
    }
     
</script>


Output : 

The String GeekforGeeks has duplicate characters

Time Complexity: O(n)  

Auxiliary Space: O(1)

Exercise: Above program is case insensitive, you can try making the same program that is case sensitive i.e Geeks and GEeks both give different output.

Using Java Stream

C++




// C++ code to implement the approach
#include <bits/stdc++.h>
using namespace std;
 
bool uniqueCharacters(string s)
{
 
  // If at any character more than once create another
  // stream stream count more than 0, return false
  for (int i = 0; i < s.size(); i++) {
    for (int j = i + 1; j < s.size(); j++) {
      if (s[i] == s[j]) {
        return false;
      }
    }
  }
  return true;
}
 
int main()
{
  string input = "GeeksforGeeks";
  if (uniqueCharacters(input))
    cout << "The String " << input
    << " has all unique characters\n";
  else
    cout << "The String " << input
    << " has duplicate characters\n";
  return 0;
}
 
// This code is contributed by phasing17


Java




import java.util.Collections;
import java.util.stream.Collectors;
class GfG {
    boolean uniqueCharacters(String s)
    {
        // If at any character more than once create another stream
        // stream count more than 0, return false
        return s.chars().filter(e-> Collections.frequency(s.chars().boxed().collect(Collectors.toList()), e) > 1).count() > 1 ? false: true;
    }
  
    public static void main(String args[])
    {
        GfG obj = new GfG();
        String input = "GeeksforGeeks";
  
        if (obj.uniqueCharacters(input))
            System.out.println("The String " + input + " has all unique characters");
        else
            System.out.println("The String " + input + " has duplicate characters");
    }
}
 
//Write Java code here


Python3




# Python3 program to implement the approach
from collections import Counter
 
def uniqueCharacters(s):
   
    # If at any character more than once create another stream
    # stream count more than 0, return false
    return not any(filter(lambda x: x > 1, list(Counter(list(s)).values())))
 
# Driver code
input = "GeeksforGeeks"
 
if uniqueCharacters(input):
    print("The String " + input + " has all unique characters")
         
else:
    print("The String " + input + " has duplicate characters")
        
# This code is contributed by phasing17


C#




// C# program to implement the approach
using System.Linq;
 
class GfG {
  public bool UniqueCharacters(string s) {
 
    // If at any character more than once create another stream
    // stream count more than 0, return false
    return s.ToCharArray().Count(e => s.Count(f => f == e) > 1) > 1 ? false : true;
  }
 
  // Driver Code
  static void Main(string[] args) {
    GfG obj = new GfG();
    string input = "GeeksforGeeks";
 
    if (obj.UniqueCharacters(input))
      System.Console.WriteLine("The String " + input + " has all unique characters");
    else
      System.Console.WriteLine("The String " + input + " has duplicate characters");
  }
}
 
// This code is contributed by Prasad Kandekar(prasad264)


Javascript




// JavaScript code to implement the approach
 
function uniqueCharacters(s)
{
    // If at any character more than once create another
    // stream stream count more than 0, return false
    let arr = s.split("");
    return !arr.some((v, i) => arr.indexOf(v) < i);
}
 
let input = "GeeksforGeeks";
 
if (uniqueCharacters(input))
    console.log("The String " + input + " has all unique characters");
else
    console.log("The String " + input + " has duplicate characters");
 
 
 
 
// This code is contributed by phasing17


Reference: 
Cracking the Coding Interview by Gayle 

Approach 5: Using sets() function:

  • Convert the string to set.
  • If the length of set is equal to the length of the string then return True else False.

Below is the implementation of the above approach

C++




// C++ program to illustrate String with unique
// characters using set data structure
#include <bits/stdc++.h>
using namespace std;
 
bool uniqueCharacters(string str)
{
    set<char> char_set;
 
    // Inserting character of string into set
    for(char c : str)
    {
        char_set.insert(c);
    }
 
    // If length of set is equal to len of string
    // then it will have unique characters
    return char_set.size() == str.size();
}
 
// Driver code
int main()
{
    string str = "GeeksforGeeks";
 
    if (uniqueCharacters(str))
    {
        cout << "The String " << str
             << " has all unique characters\n";
    }
    else
    {
        cout << "The String " << str
             << " has duplicate characters\n";
    }
    return 0;
}
 
// This code is contributed by abhishekjha558498


Java




// Java program to illustrate String with unique
// characters using set data structure
import java.util.*;
 
class GFG{
 
static boolean uniqueCharacters(String str)
{
    HashSet<Character> char_set = new HashSet<>();
 
    // Inserting character of String into set
    for(int c  = 0; c< str.length();c++)
    {
        char_set.add(str.charAt(c));
    }
 
    // If length of set is equal to len of String
    // then it will have unique characters
    return char_set.size() == str.length();
}
 
// Driver code
public static void main(String[] args)
{
    String str = "GeeksforGeeks";
 
    if (uniqueCharacters(str))
    {
        System.out.print("The String " +  str
            + " has all unique characters\n");
    }
    else
    {
        System.out.print("The String " +  str
            + " has duplicate characters\n");
    }
}
}
 
 
// This code contributed by umadevi9616


Python3




# Python3 program to illustrate String with unique
# characters
def uniqueCharacters(str):
   
    # Converting string to set
    setstring = set(str)
     
    # If length of set is equal to len of string
    # then it will have unique characters
    if(len(setstring) == len(str)):
        return True
       
    return False
 
 
# Driver Code
if __name__ == '__main__':
 
    input = "GeeksforGeeks"
 
    if (uniqueCharacters(input)):
        print("The String " + input +
              " has all unique characters")
    else:
        print("The String " + input +
              " has duplicate characters")
 
# This code is contributed by vikkycirus


C#




// C# program to illustrate String with unique
// characters using set data structure
using System;
using System.Collections.Generic;
 
public class GFG {
 
    static bool uniquechars(String str)
    {
        HashSet<char> char_set = new HashSet<char>();
 
        // Inserting character of String into set
        for (int c = 0; c < str.Length; c++) {
            char_set.Add(str);
        }
 
        // If length of set is equal to len of String
        // then it will have unique characters
        if (char_set.Count == str.Length) {
            return true;
        }
        else {
            return false;
        }
    }
 
    // Driver code
    public static void Main(String[] args)
    {
        String str = "GeeksforGeeks";
 
        if (uniquechars(str)) {
            Console.Write("The String " + str
                          + " has all unique characters\n");
        }
        else {
            Console.Write("The String " + str
                          + " has duplicate characters\n");
        }
    }
}
 
// This code is contributed by umadevi9616


Javascript




<script>
 
// Function program to illustrate String
// with unique characters
function uniqueCharacters(str)
{
     
    // Converting string to set
    var setstring = new Set(str)
     
    // If length of set is equal to len of string
    // then it will have unique characters
    if (setstring.size == str.length)
    {
        return true
    }
    else
    {
        return false
    }
}
 
// Driver Code
var input = "GeeksforGeeks"
 
if (uniqueCharacters(input))
{
    document.write("The String " + input +
                   " has all unique characters") ;
}
else
{
    document.write("The String " + input +
                   " has duplicate characters")
}
 
// This code is contributed by bunnyram19
 
</script>


Output:

The String GeeksforGeeks has duplicate characters

Time Complexity: O(nlogn)

Auxiliary Space: O(n)



Last Updated : 10 Feb, 2023
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