Tree

Tree

Tree is a widely used abstract data type (ADT)—or data structure implementing this ADT—that simulates a hierarchical tree structure, with a root value and subtrees of children with a parent node, represented as a set of linked nodes.

A tree data structure can be defined recursively (locally) as a collection of nodes (starting at a root node), where each node is a data structure consisting of a value, together with a list of references to nodes (the "children"), with the constraints that no reference is duplicated, and none points to the root.

Source: Wikipedia page for Tree

Kotlin playground link

Code

class TreeNode<T>(value: T) {
    var value: T = value

    var parent: TreeNode<T>? = null

    var children: MutableList<TreeNode<T>> = mutableListOf()

    fun addChild(node: TreeNode<T>) {
        children.add(node)
        node.parent = this
    }

    override fun toString(): String {
        var s = "$value"
        if (children.isNotEmpty()) {
            s += " {" + children.map { it.toString() } + " }"
        }
        return s
    }
}