function depthFirstSearch<T>(node : Node<T> | null, target: T) : Node<T> | null
{
    if (!node) return null;
    if (node.value === target)
        return node;
    
    const left = depthFirstSearch(node.left, target);
    if (left != null)
        return left;

    const right = depthFirstSearch(node.right, target);
    return right;
}