Traverse to the deepest using Java

Question

I have a data structure like below:

Task(id,name,subTasks[Task])

But the problem is the subTasks can contain Tasks which have another subTa

Answer 1

Use Guava TreeTraverser:

Task root = ...

/*
 * For example, you have the following tree:
 *
 *          h
 *        / | \
 *       /  e  \
 *      d       g
 *     /|\      |
 *    / | \     f
 *   a  b  c        
 */

TreeTraverser<Task> traverser = new TreeTraverser<Task>() {
    @Override
    public Iterable<Task> children(Task root) {
        return root.subTasks;
    }
};

Then you can iterate over the tree with for loop in several ways:

// Iterate in breadth-first order (hdegabcf)
for (Task task : traverser.breadthFirstTraversal(root)) { ... }

or

// Iterate in preorder (hdabcegf)
for (Task task : traverser.preOrderTraversal(root)) { ... }

or

// Iterate in postorder (abcdefgh)
for (Task task : traverser.postOrderTraversal(root)) { ... }

Answer 2

Data structure: the implicit tree formed by object references.

Traversal: recursion or queues.

However, you will have to consider each use case individually. Some will call for depth-first traversal, some for breadth-first traversal. Consider using some graph library to build the trees in the first place if you need a lot of graph operations.