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Given a word or phrase, check if it is an isogram or not. An Isogram is a word in which no letter occurs more than once

Examples: 

Input: Machine
Output: True
Explanation: “Machine” does not have any character repeating, it is an Isogram

Input : Geek
Output : False
Explanation: “Geek” has ‘e’ as repeating character, it is not an Isogram

Check if a string is Isogram or not using sorting:

To solve the problem follow the below idea:

Sort the string and for every character check, if the current character is equal to the previous character or not. If it is equal then the string is not an isogram

Follow the given steps to solve the problem:

  • Convert the string into lowercase English letters
  • Sort the string
  • Traverse the string and check for every character
    • If the current character is equal to the character on the previous index then return false
  • Return true

Below is the implementation of the above approach:

C++




// C++ program to check
// If a given string is isogram or not
#include <bits/stdc++.h>
using namespace std;
 
// Function to check
// If a given string is isogram or not
string is_isogram(string str)
{
    int len = str.length();
 
    // Convert the string in lower case letters
    for (int i = 0; i < len; i++)
        str[i] = tolower(str[i]);
 
    sort(str.begin(), str.end());
 
    for (int i = 0; i < len; i++) {
        if (str[i] == str[i + 1])
            return "False";
    }
    return "True";
}
 
// Driver code
int main()
{
    string str1 = "Machine";
   
      // Function call
    cout << is_isogram(str1) << endl;
 
    string str2 = "isogram";
   
      // Function call
    cout << is_isogram(str2) << endl;
 
    string str3 = "GeeksforGeeks";
   
      // Function call
    cout << is_isogram(str3) << endl;
 
    string str4 = "Alphabet";
   
      // Function call
    cout << is_isogram(str4) << endl;
 
    return 0;
}
 
// Contributed by nuclode


Java




// Java program to check
// if a given string is isogram or not
import java.io.*;
import java.util.*;
 
class GFG {
    // Function to check
    // if a given string is isogram or not
    static boolean is_isogram(String str)
    {
        // Convert the string in lower case letters
        str = str.toLowerCase();
        int len = str.length();
 
        char arr[] = str.toCharArray();
 
        Arrays.sort(arr);
        for (int i = 0; i < len - 1; i++) {
            if (arr[i] == arr[i + 1])
                return false;
        }
        return true;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        String str1 = "Machine";
       
          // Function call
        System.out.println(is_isogram(str1));
 
        String str2 = "isogram";
       
          // Function call
        System.out.println(is_isogram(str2));
 
        String str3 = "GeeksforGeeks";
       
          // Function call
        System.out.println(is_isogram(str3));
 
        String str4 = "Alphabet";
       
          // Function call
        System.out.println(is_isogram(str4));
    }
}
 
// Contributed by Pramod Kumar


Python3




# Python program to check
# if a word is isogram or not
 
 
def is_isogram(word):
 
    # Convert the word or sentence in lower case letters.
    clean_word = word.lower()
 
    # Make an empty list to append unique letters
    letter_list = []
 
    for letter in clean_word:
 
        # If letter is an alphabet then only check
        if letter.isalpha():
            if letter in letter_list:
                return False
            letter_list.append(letter)
 
    return True
 
# Driver code
if __name__ == '__main__':
   
      # Function call
    print(is_isogram("Machine"))
    print(is_isogram("isogram"))
    print(is_isogram("GeeksforGeeks"))
    print(is_isogram("Alphabet "))


C#




// C# program to check if a given
// string is isogram or not
using System;
 
public class GFG {
     
    // Function to check if a given
    // string is isogram or not
    static bool is_isogram(string str)
    {
        // Convert the string in lower case letters
        str = str.ToLower();
        int len = str.Length;
 
        char[] arr = str.ToCharArray();
 
        Array.Sort(arr);
        for (int i = 0; i < len - 1; i++) {
            if (arr[i] == arr[i + 1])
                return false;
        }
        return true;
    }
 
    // Driver code
    public static void Main()
    {
        string str1 = "Machine";
       
          // Function call
        Console.WriteLine(is_isogram(str1));
 
        string str2 = "isogram";
       
          // Function call
        Console.WriteLine(is_isogram(str2));
 
        string str3 = "GeeksforGeeks";
       
          // Function call
        Console.WriteLine(is_isogram(str3));
 
        string str4 = "Alphabet";
       
          // Function call
        Console.WriteLine(is_isogram(str4));
    }
}
 
// This code is contributed by Sam007


Javascript




<script>
    // Javascript program to check if a given
    // string is isogram or not
     
    // Function to check if a given
    // string is isogram or not
    function is_isogram(str)
    {
        // Convert the string in lower case letters
        str = str.toLowerCase();
        let len = str.length;
  
        let arr = str.split('');
  
        arr.sort();
        for (let i = 0; i < len - 1; i++) {
            if (arr[i] == arr[i + 1])
                return false;
        }
        return true;
    }
     
    let str1 = "Machine";
    if(is_isogram(str1))
    {
        document.write("True" + "</br>");
    }
    else{
        document.write("False" + "</br>");
    }
 
    let str2 = "isogram";
    if(is_isogram(str2))
    {
        document.write("True" + "</br>");
    }
    else{
        document.write("False" + "</br>");
    }
 
    let str3 = "GeeksforGeeks";
    if(is_isogram(str3))
    {
        document.write("True" + "</br>");
    }
    else{
        document.write("False" + "</br>");
    }
 
    let str4 = "Alphabet";
    if(is_isogram(str4))
    {
        document.write("True" + "</br>");
    }
    else{
        document.write("False" + "</br>");
    }
     
    // This code is contributed by suresh07.
</script>


Output

True
True
False
False

Time Complexity: O(N log N)
Auxiliary Space: O(1)

Check if a string is Isogram or not using Hash-Map:

To solve the problem follow the below idea:

In this, the count of characters of the string is stored in the hashmap, and wherever it is found to be greater than 1 for any char, return false else return true at the end

Follow the given steps to solve the problem:

  • Declare a hashmap to store the count of the characters of the string
  • Traverse the string
    • Increase the count of the current character in the hashmap
    • If the count of the current character is greater than one then return false
  • Return true

Below is the implementation of the above approach:

C++




// CPP code to check string is isogram or not
#include <bits/stdc++.h>
 
using namespace std;
 
// function to check isogram
bool check_isogram(string str)
{
 
    int length = str.length();
    int mapHash[26] = { 0 };
 
    // loop to store count of chars and check if it is
    // greater than 1
    for (int i = 0; i < length; i++) {
        mapHash[str[i] - 'a']++;
 
        // if count > 1, return false
        if (mapHash[str[i] - 'a'] > 1) {
            return false;
        }
    }
 
    return true;
}
 
// Driver code
int main()
{
    string str = "geeks";
    string str2 = "computer";
 
    // checking str as isogram
    if (check_isogram(str)) {
        cout << "True" << endl;
    }
    else {
        cout << "False" << endl;
    }
 
    // checking str2 as isogram
    if (check_isogram(str2)) {
        cout << "True" << endl;
    }
    else {
        cout << "False" << endl;
    }
 
    return 0;
}


Java




// Java code to check string is isogram or not
import java.io.*;
 
class GFG {
 
    // function to check isogram
    static boolean check_isogram(String str)
    {
 
        int length = str.length();
        int mapHash[] = new int[26];
 
        // loop to store count of chars and
        // check if it is greater than 1
        for (int i = 0; i < length; i++) {
            mapHash[str.charAt(i) - 'a']++;
 
            // if count > 1, return false
            if (mapHash[str.charAt(i) - 'a'] > 1) {
                return false;
            }
        }
 
        return true;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        String str = "geeks";
        String str2 = "computer";
 
        // checking str as isogram
        if (check_isogram(str))
            System.out.println("True");
        else
            System.out.println("False");
 
        // checking str2 as isogram
        if (check_isogram(str2))
            System.out.println("True");
        else
            System.out.println("False");
    }
}
 
// This code contributed by Rajput-Ji


Python3




# Python3 code to check string is isogram or not
 
# function to check isogram
 
 
def check_isogram(string):
 
    length = len(string)
    mapHash = [0] * 26
 
    # loop to store count of chars
    # and check if it is greater than 1
    for i in range(length):
 
        mapHash[ord(string[i]) - ord('a')] += 1
 
        # if count > 1, return false
        if (mapHash[ord(string[i]) - ord('a')] > 1):
 
            return False
 
    return True
 
 
# Driver code
if __name__ == "__main__":
 
    string = "geeks"
    string2 = "computer"
 
    # checking str as isogram
    if (check_isogram(string)):
        print("True")
    else:
        print("False")
 
    # checking str2 as isogram
    if (check_isogram(string2)):
        print("True")
 
    else:
        print("False")
 
# This code is contributed by AnkitRai01


C#




// C# code to check string is isogram or not
using System;
public class GFG {
 
    // function to check isogram
    static bool check_isogram(String str)
    {
 
        int length = str.Length;
        int[] mapHash = new int[26];
 
        // loop to store count of chars and
        // check if it is greater than 1
        for (int i = 0; i < length; i++) {
            mapHash[str[i] - 'a']++;
 
            // if count > 1, return false
            if (mapHash[str[i] - 'a'] > 1) {
                return false;
            }
        }
 
        return true;
    }
 
    // Driver code
    public static void Main(String[] args)
    {
        String str = "geeks";
        String str2 = "computer";
 
        // checking str as isogram
        if (check_isogram(str))
            Console.WriteLine("True");
        else
            Console.WriteLine("False");
 
        // checking str2 as isogram
        if (check_isogram(str2))
            Console.WriteLine("True");
        else
            Console.WriteLine("False");
    }
}
 
// This code has been contributed by 29AjayKumar


Javascript




<script>
    // Javascript code to check string is isogram or not
     
    // function to check isogram
    function check_isogram(str)
    {
 
        let length = str.length;
        let mapHash = new Array(26);
        mapHash.fill(0);
 
        // loop to store count of chars and
        // check if it is greater than 1
        for (let i = 0; i < length; i++)
        {
            mapHash[str[i].charCodeAt() - 'a'.charCodeAt()]++;
 
            // if count > 1, return false
            if (mapHash[str[i].charCodeAt() - 'a'.charCodeAt()] > 1)
            {
                return false;
            }
        }
 
        return true;
    }
     
    let str = "geeks";
    let str2 = "computer";
    
    // checking str as isogram
    if (check_isogram(str))
        document.write("True" + "</br>");
    else
        document.write("False" + "</br>");
    
    // checking str2 as isogram
    if (check_isogram(str2))
          document.write("True" + "</br>");
    else
        document.write("False" + "</br>");
     
    // This code is contributed by divyeshrabadiya07.
</script>


Output

False
True

Time Complexity: O(N)
Auxiliary Space: O(1), as an array of fixed size 26 is used.

Thanks Sahil Bansal for suggesting the above method. 
If you like GeeksforGeeks (We know you do!) and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org.



Last Updated : 19 Sep, 2022
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