findArrayUnion()

Step 1: Understand the Problem

The first thing we need to do is understand the problem. We want to write a function that takes two arrays as arguments and returns an array that contains the union of these arrays. The union of two arrays is a set containing distinct elements from both arrays. In other words, if an element appears in either of the two input arrays, it should appear in the returned array.

public static int[] arrayUnion(int[] array1, int[] array2) {
  // TODO: implement function
}

Step 2: Plan the Solution

We should start by creating a new array that is large enough to hold all elements from both input arrays. After that, we should iterate through both input arrays to collect all distinct elements.

Step 3: Implementing the Collection of Elements

Now, we start working on collecting all distinct elements from both arrays. We use a HashSet to store these elements as it automatically removes duplicates.

public static int[] arrayUnion(int[] array1, int[] array2) {
  HashSet<Integer> set = new HashSet<>();

  for(int i : array1) {
    set.add(i);
  }

  for(int i : array2) {
    set.add(i);
  }
}

Step 4: Returning the Result

After we've collected all distinct elements in the HashSet, we need to convert this set back to an array and return it.

public static int[] arrayUnion(int[] array1, int[] array2) {
  HashSet<Integer> set = new HashSet<>();

  for(int i : array1) {
    set.add(i);
  }

  for(int i : array2) {
    set.add(i);
  }

  int[] result = new int[set.size()];

  int index = 0;

  for(int i : set) {
    result[index++] = i;
  }

  return result;
}

Conclusion

That's it! Now we have a function that correctly handles the union of two arrays. It uses a HashSet to remove duplicates, ensuring we only get distinct elements in the returned array.