Stack

Stack

Stack is an abstract data type that serves as a collection of elements, with two principal operations: push, which adds an element to the collection, and pop, which removes the most recently added element that was not yet removed. The order in which elements come off a stack gives rise to its alternative name, LIFO (for last in, first out). Additionally, a peek operation may give access to the top without modifying the stack.

The code

class Stack<T:Comparable<T>>(list:MutableList<T>) {

    var items: MutableList<T> = list


    fun isEmpty():Boolean = this.items.isEmpty()

    fun count():Int = this.items.count()

    fun push(element:T) {
        val position = this.count()
        this.items.add(position, element)
    }

    override  fun toString() = this.items.toString()

    fun pop():T? {
        if (this.isEmpty()) {
            return null
        } else {
            val item =  this.items.count() - 1
            return this.items.removeAt(item)
        }
    }

    fun peek():T? {
        if (isEmpty()) {
            return null
        } else {
            return this.items[this.items.count() - 1]
        }
    }

}