Paths With A Given Sum

    private List<Tree<E>> traverseTreeWithBfs(){
        Deque<Tree<E>> queue = new ArrayDeque<>();

        queue.offer(this);

        List<Tree<E>> allNodes = new ArrayList<>();

        while(!queue.isEmpty()){
            Tree<E> tree = queue.poll();

            allNodes.add(tree);

            for (Tree<E> child : tree.children) {
                queue.offer(child);
            }
        }

        return allNodes;
    }

    private boolean isLeaf() {
        return this.parent != null && this.children.size() == 0;
    }

    @Override
    public List<List<E>> pathsWithGivenSum(int sum) {
        List<Tree<E>> trees = this.traverseTreeWithBfs();

        List<E> goodPath = new ArrayList<>();
        List<List<E>> result = new ArrayList<>();

        int currentSum;

        for(Tree<E> tree : trees){
            goodPath.clear();
            currentSum = 0;

            if(tree.isLeaf()){
                while(tree.parent != null){
                    currentSum += (Integer) tree.getKey();
                    goodPath.add(tree.getKey());
                    tree = tree.parent;
                }

                currentSum += (Integer) tree.getKey();
                goodPath.add(tree.getKey());
            }

            if(currentSum == sum){
                Collections.reverse(goodPath);
                result.add(goodPath);
            }
        }

        return result;
    }