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nicmart/Tree

nicmart/Tree

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Last Updated: 2023-09-14 11:28:18

#php #data-structrues #tree

A basic but flexible tree data structure for php and a fluent tree builder implementation.

License: MIT License

Languages: PHP, Makefile

Tree

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In Tree you can find a basic but flexible tree data structure for php together with and an handful Builder class, that enables you to build tree in a fluent way.

The tree data structure

The Tree\Node\NodeInterface interface abstracts the concept of a tree node. In Tree a Node has essentially two things: a set of children (that implements the same NodeInterface interface) and a value.

On the other hand, the Tree\Node\Node gives a straight implementation for that interface.

Creating a node

use Tree\Node\Node;

$node = new Node('foo');

Getting and setting the value of a node

Each node has a value property, that can be any php value.

$node->setValue('my value');
echo $node->getValue(); //Prints 'my value'

Adding one or more children

$child1 = new Node('child1');
$child2 = new Node('child2');

$node
    ->addChild($child1)
    ->addChild($child2);

Removing a child

$node->removeChild($child1);

Getting the array of all children

$children = $node->getChildren();

Overwriting the children set

$node->setChildren([new Node('foo'), new Node('bar')]);

Removing all children

$node->removeAllChildren();

Getting if the node is a leaf or not

A leaf is a node with no children.

$node->isLeaf();

Getting if the node is a child or not

A child is a node that has a parent.

$node->isChild();

Getting the parent of a node

Reference to the parent node is automatically managed by child-modifiers methods

$root->addChild($node = new Node('child'));
$node->getParent(); // Returns $root

Getting the ancestors of a node

$root = (new Node('root'))
    ->addChild($child = new Node('child'))
    ->addChild($grandChild = new Node('grandchild'))
;

$grandchild->getAncestors(); // Returns [$root, $child]

Related Methods

  • getAncestorsAndSelf retrieves ancestors of a node with the current node included.

Getting the root of a node

$root = $node->root();

Getting the neighbors of a node

$root = (new Node('root'))
    ->addChild($child1 = new Node('child1'))
    ->addChild($child2 = new Node('child2'))
    ->addChild($child3 = new Node('child3'))
;

$child2->getNeighbors(); // Returns [$child1, $child3]

Related Methods

  • getNeighborsAndSelf retrieves neighbors of current node and the node itself.

Getting the number of nodes in the tree

$node->getSize();

Getting the depth of a node

$node->getDepth();

Getting the height of a node

$node->getHeight();

The Builder

The builder provides a convenient way to build trees. It is provided by the Builder class, but you can implement your own builder making an implementation of the BuilderInterfaceclass.

Example

Let's see how to build the following tree, where the nodes label are represents nodes values:

       A
      / \
     B   C
        /|\
       D E F
      /|
     G H

And here is the code:

$builder = new Tree\Builder\NodeBuilder;

$builder
    ->value('A')
    ->leaf('B')
    ->tree('C')
        ->tree('D')
            ->leaf('G')
            ->leaf('H')
            ->end()
        ->leaf('E')
        ->leaf('F')
        ->end()
;

$nodeA = $builder->getNode();

The example should be self-explanatory, but here you are a brief description of the methods used above.

Builder::value($value)

Set the value of the current node to $value

Builder::leaf($value)

Add to the current node a new child whose value is $value.

Builder::tree($value)

Add to the current node a new child whose value is $value, and set the new node as the builder current node.

Builder::end()

Returns to the context the builder was before the call to treemethod, i.e. make the builder go one level up.

Builder::getNode()

Returns the current node.

Traversing a tree

Yield

You can obtain the yield of a tree (i.e. the list of leaves in a pre-order traversal) using the YieldVisitor.

For example, if $node is the tree built above, then

use Tree\Visitor\YieldVisitor;

$visitor = new YieldVisitor;

$yield = $node->accept($visitor);
// $yield will contain nodes B, G, H, E, F

Pre-order Traversal

You can walk a tree in pre-order:

use Tree\Visitor\PreOrderVisitor;

$visitor = new PreOrderVisitor;

$yield = $node->accept($visitor);
// $yield will contain nodes A, B, C, D, G, H, E, F

Post-order Traversal

You can walk a tree in post-order:

use Tree\Visitor\PostOrderVisitor;

$visitor = new PostOrderVisitor;

$yield = $node->accept($visitor);
// $yield will contain nodes B, G, H, D, E, F, C, A

Install

Run

$ composer require nicmart/tree

Tests

phpunit

Changelog

Please have a look at CHANGELOG.md.

Contributing

Please have a look at CONTRIBUTING.md.

License

This package is licensed using the MIT License.

Please have a look at LICENSE.md.

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