Question

Assume ArrayList<E> arrayBinaryTree = new ArrayList<E>( ) is used to store a binary tree. The root node is stored at the cell whose index is 0 (first element in the array). Providing a method with signature public boolean isInternal (int target)  to check if the element stored at cell target (refers to an index) is an internal node or not. Return true for yes and false for no.

Answer 1

public boolean isInternal(int target) {
    int left = 2 * target + 1, right = 2 * target + 2;
    return target > 0 && target < arrayBinaryTree.size()
            && ((left < arrayBinaryTree.size() && arrayBinaryTree.get(left) != null)
            || (right < arrayBinaryTree.size() && arrayBinaryTree.get(right) != null))
            && arrayBinaryTree.get(target) != null;
}