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

The 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.isEmpty()) {
            s += " {" + children.map { it.toString() } + " }"
        }
        return s
    }
}