diff --git a/src/CommonElementsFinder.java b/src/CommonElementsFinder.java
index fb88a4b..0c66265 100644
--- a/src/CommonElementsFinder.java
+++ b/src/CommonElementsFinder.java
@@ -1,3 +1,4 @@
+import java.util.HashSet;
 import java.util.Set;
 
 /**
@@ -11,17 +12,29 @@ public class CommonElementsFinder {
      *
      * @param array1 the first array of integers
      * @param array2 the second array of integers
-     * @return a Set<Integer> containing the integers that are present in both arrays
+     * @return a Set<Integer> containing the integers that are present in both
+     *         arrays
      */
     public static Set<Integer> findCommonElements(int[] array1, int[] array2) {
-        // TODO
-        return null;
-    }
+        Set<Integer> set1 = new HashSet<>();
+        Set<Integer> common = new HashSet<>();
+
+        for (int num : array1) {
+            set1.add(num);
+        }
 
+        for (int num : array2) {
+            if (set1.contains(num)) {
+                common.add(num);
+            }
+        }
+
+        return common;
+    }
 
     public static void main(String[] args) {
-        int[] array1 = {1, 2, 3, 4, 5};
-        int[] array2 = {4, 5, 6, 7, 8};
+        int[] array1 = { 1, 2, 3, 4, 5 };
+        int[] array2 = { 4, 5, 6, 7, 8 };
 
         Set<Integer> common = findCommonElements(array1, array2);
         System.out.println("Common elements: " + common);
diff --git a/src/DuplicateRemover.java b/src/DuplicateRemover.java
index 8d70003..0b93825 100644
--- a/src/DuplicateRemover.java
+++ b/src/DuplicateRemover.java
@@ -1,4 +1,7 @@
+import java.util.ArrayList;
 import java.util.List;
+import java.util.Set;
+import java.util.TreeSet;
 
 /**
  * The DuplicateRemover class provides a method to remove duplicate words
@@ -7,19 +10,25 @@
 public class DuplicateRemover {
 
     /**
-     * Removes duplicate words from the input array, sorts them in lexicographic order,
+     * Removes duplicate words from the input array, sorts them in lexicographic
+     * order,
      * and returns a list of unique words.
      *
      * @param words an array of strings that may contain duplicate words
      * @return a sorted List<String> containing unique words from the input array
      */
     public static List<String> sortAndRemoveDuplicates(String[] words) {
-        // TODO
-        return null;
+        Set<String> sortedSet = new TreeSet<>();
+
+        for (String word : words) {
+            sortedSet.add(word);
+        }
+
+        return new ArrayList<>(sortedSet);
     }
 
     public static void main(String[] args) {
-        String[] words = {"yes", "no", "maybe", "yes", "yes"};
+        String[] words = { "yes", "no", "maybe", "yes", "yes" };
         List<String> uniqueWords = sortAndRemoveDuplicates(words);
         System.out.println(uniqueWords);
     }
diff --git a/src/UniqueCharacterChecker.java b/src/UniqueCharacterChecker.java
index 554ffc4..3e69e77 100644
--- a/src/UniqueCharacterChecker.java
+++ b/src/UniqueCharacterChecker.java
@@ -1,3 +1,6 @@
+import java.util.HashSet;
+import java.util.Set;
+
 /**
  * The UniqueCharacterChecker class provides a method to check if all characters
  * in a given word are unique.
@@ -12,9 +15,20 @@ public class UniqueCharacterChecker {
      */
     public static boolean hasUniqueCharacters(String word) {
         // TODO: implement this!
-        // Requirement: This must run in O(n) time, where n is the number of characters in the word
+        // Requirement: This must run in O(n) time, where n is the number of characters
+        // in the word
         // Hint: Stuck? Consider looking up "charAt" and seeing how it can help you
-        return false;
+        Set<Character> seen = new HashSet<>();
+
+        for (int i = 0; i < word.length(); i++) {
+            char c = word.charAt(i);
+            if (seen.contains(c)) {
+                return false;
+            }
+            seen.add(c);
+        }
+
+        return true;
     }
 
     public static void main(String[] args) {