MyStack.kt

package io.dahgan

/**
 * Stack is a data structure that stores some elements and these elements can be received in LIFO order.
 * That means the last element that is pushed to stack would be the first one that can be poped. 
 * 
 * Our stack has a limited capacity and can not store element more than its capacity.
 * 
 * Note to developer: 
 *     - define an array of integers to keep the stack elements. 
 *     - you can initialize the array with (0) in the beginning
 *     - define a variable "top" to keep the index of last element that has been added to stack. ( -1 in the beginning )
 */
class MyStack(capacity: Int) {

    /**
     * Adds the given number to the stack
     * @return true if the push was successful, false if the stack was full
     */
    fun push(n: Int): Boolean = false

    /**
     * Removes the last element in the stack and returns it. 
     * @return the last element in the stack, -1 if the stack is empty
     */
    fun pop(): Int = -1

    /**
     * Returns the last element in the stack WITHOUT removing it.
     * @return the last element in the stack, -1 if the stack is empty
     */
    fun peek(): Int = -1

    /**
     * Checks if the stack is empty.
     * @return true if the stack is empty, false otherwise
     */
    fun isEmpty(): Boolean = false

    /**
     * Checks if the stack capacity is full.
     * @return true if the stack is full, false otherwise
     */
    fun isFull(): Boolean = false
}