Distinct characters in a string

Created on: Jan 16, 2025

Input  : Geeks for Geeks
Output : for

Input  : Hello Geeks
Output : HoGks

import java.util.List;
import java.util.stream.Collectors;

public class Solution {
    public static List<Character> uniqueChar(String str) {
       return null;
    }

    public static void main(String[] args) {

        boolean test = true;
        test = test && test == uniqueChar("aabdcce").equals(List.of('b', 'd', 'e'));


        // Test Case 1: All unique characters
        test = test && uniqueChar("abcdef").equals(List.of('a', 'b', 'c', 'd', 'e', 'f'));

        // Test Case 2: All characters repeated
        test = test && uniqueChar("aabbccdd").equals(List.of());

        // Test Case 3: Mixed unique and repeated characters
        test = test && uniqueChar("aabbcdee").equals(List.of('c', 'd'));

        // Test Case 4: String with spaces
        test = test && uniqueChar("a b c a b").equals(List.of('c'));

        // Test Case 5: Empty string
        test = test && uniqueChar("").equals(List.of());

        // Test Case 6: String with a single character
        test = test && uniqueChar("z").equals(List.of('z'));

        // Test Case 7: String with special characters
        test = test && uniqueChar("@#@!$!").equals(List.of('#', '$'));

        // Test Case 8: Large string with repeated patterns
        String largeString = "abc".repeat(1000) + "xyz";
        List<Character> expectedLarge = List.of('x', 'y', 'z');
        test = test && uniqueChar(largeString).equals(expectedLarge);

        // Test Case 9: Unicode characters
        test = test && uniqueChar("a😀b😀c").equals(List.of('a', 'b', 'c'));

        if (test) {
            System.out.println("pass");
        } else {
            System.out.println("Fail");
        }
    }
}

Solution

public static List<Character> uniqueChar(String str) {
    return str.chars().mapToObj(obj->(char)obj)
            .filter(c->str.indexOf(c)==str.lastIndexOf(c))
            .collect(Collectors.toList());
}

Reference

geeksforgeeks