Algorithms – Part 6: Finding Isograms

Problem:

Check if a String is an Isogram – You need to check if a given string is an isogram, considering only alphabetical characters and ignoring case sensitivity. This problem involves checking for duplicate characters within a string, similar to how you check for palindrome characters within a string in the original palindrome problem.

Code:

import java.util.HashSet;
import java.util.Set;

public class IsogramChecker {
    public static boolean isIsogram(String str) {
        // Convert the string to lowercase to ignore case sensitivity
        str = str.toLowerCase();
        
        // Use a set to keep track of seen characters
        Set<Character> seen = new HashSet<>();
        
        for (char ch : str.toCharArray()) {
            // If the character is not alphabetical, ignore it
            if (!Character.isLetter(ch)) {
                continue;
            }
            
            // If the character is already in the set, it's not an isogram
            if (seen.contains(ch)) {
                return false;
            }
            
            // Otherwise, add it to the set
            seen.add(ch);
        }
        
        // If we've checked all characters and haven't found duplicates, it's an isogram
        return true;
    }

    public static void main(String[] args) {
        String str1 = "abcdef";
        String str2 = "programming";
        String str3 = "hello";

        System.out.println("Is str1 an isogram? " + isIsogram(str1)); // Output: true
        System.out.println("Is str2 an isogram? " + isIsogram(str2)); // Output: false
        System.out.println("Is str3 an isogram? " + isIsogram(str3)); // Output: false
    }
}