In this source code example, we will write a code to implement the Stack data structure using the Kotlin programming language.
A stack is an ordered list in which insertion and deletion are done at one end, called a top. The last element inserted is the first one to be deleted. Hence, it is called the Last in First out (LIFO) or First in Last out (FILO) list.
Stack Implementation in Kotlin
Main stack operations
Push Operation:
The process of putting a new data element onto the stack is known as a Push Operation.
Pop Operation:
Accessing the content while removing it from the stack, is known as a Pop Operation.
Let's Implement Linked List to perform the below operations:
push()pushAll()pop()peek()isEmptyisFull()
Here is the complete code implement Stack in Kotlin:
import java.util.Arrays
class Stack<E> {
private val minCapacityIncrement = 12
private var elements: Array<Any?>
private var size = 0
constructor() {
this.elements = arrayOf()
}
constructor(initialCapacity: Int) {
this.elements = arrayOfNulls(initialCapacity)
}
constructor(elements: Array<E>) {
this.elements = elements as Array<Any?>
size += elements.size
}
fun push(element: E) {
if (size == elements.size) {
val newArray = arrayOfNulls<Any>(size + if (size < minCapacityIncrement / 2)
minCapacityIncrement
else
size shr 1)
System.arraycopy(elements, 0, newArray, 0, size)
elements = newArray
}
elements[size++] = element
}
fun pushAll(newElements: Array<E>) {
val newSize = size + newElements.size
if (elements.size < newSize) {
// New sizing can be of any logic as per requirement
val newArray = arrayOfNulls<Any>(newSize + minCapacityIncrement)
System.arraycopy(elements, 0, newArray, 0, size)
elements = newArray
}
System.arraycopy(newElements, 0, elements, size, newElements.size)
size = newSize
}
fun pop(): E {
if (size == 0) throw StackUnderflowException()
val index = --size
val obj = elements[index]
elements[index] = null
return obj as E
}
fun pop(count: Int) {
if (size == 0 || size < count) throw StackUnderflowException()
for (i in 0 until count) {
elements[--size] = null
}
}
fun peek() = try {
elements[size - 1] as E
} catch (e: IndexOutOfBoundsException) {
throw StackUnderflowException();
}
fun isEmpty() = size == 0
fun isFull() = size == elements.size
override fun toString(): String {
if (size == 0) return "[]"
val length = size - 1
val builder = StringBuilder(size * 16)
builder.append('[')
for (i in 0 until length) {
builder.append(elements[i])
builder.append(", ")
}
builder.append(elements[length])
builder.append(']')
return builder.toString()
}
}
class StackUnderflowException : RuntimeException()
inline fun <reified T> stackOf(vararg elements: T) = Stack<T>(elements as Array<T>)
fun main(args: Array<String>) {
val animals = Stack<String>(10)
System.out.println("$animals - Empty? -- ${animals.isEmpty()}")
animals.push("Lion")
System.out.println("$animals - Empty? -- ${animals.isEmpty()}")
animals.push("Tiger")
System.out.println("$animals - Empty? -- ${animals.isEmpty()}")
animals.push("Crocodile")
animals.push("Cat")
animals.push("Dog")
animals.push("Cow")
animals.push("Cangaroo")
animals.push("Rat")
animals.push("Bull")
System.out.println("$animals - Empty? -- ${animals.isEmpty()}")
animals.push("Ox")
System.out.println("$animals - Empty? -- ${animals.isEmpty()}")
animals.push("Zebra")
System.out.println("$animals - Empty? -- ${animals.isEmpty()}")
animals.pop()
System.out.println("$animals - Empty? -- ${animals.isEmpty()}")
println()
val languages = Stack(arrayOf("Kotlin", "Java"))
println("$languages - Empty? -- ${languages.isEmpty()}")
languages.push("C")
println("$languages - Empty? -- ${languages.isEmpty()}")
languages.pop()
println("$languages - Empty? -- ${languages.isEmpty()}")
languages.pop()
println("$languages - Empty? -- ${languages.isEmpty()}")
languages.pop()
println("$languages - Empty? -- ${languages.isEmpty()}")
testPushAll()
testPop()
testStackOf()
}
fun testPushAll() {
println()
println("Testing pushAll")
val numbers = Stack<Int>(10)
numbers.pushAll(Array<Int>(100) { i -> i })
println(numbers)
numbers.pop()
numbers.pushAll(arrayOf(1, 2, 12, 909))
println(numbers)
}
fun testPop() {
println()
println("Testing pop count")
val numbers = Stack<Int>(10)
numbers.pushAll(Array<Int>(100) { i -> i })
println(numbers)
numbers.pop(20)
numbers.pushAll(arrayOf(1, 2, 12, 909))
println(numbers)
}
fun testStackOf() {
val languages = stackOf("Kotlin", "Java")
println(languages)
languages.push("C")
println(languages)
languages.pop()
println(languages)
}
Output:
[] - Empty? -- true
[Lion] - Empty? -- false
[Lion, Tiger] - Empty? -- false
[Lion, Tiger, Crocodile, Cat, Dog, Cow, Cangaroo, Rat, Bull] - Empty? -- false
[Lion, Tiger, Crocodile, Cat, Dog, Cow, Cangaroo, Rat, Bull, Ox] - Empty? -- false
[Lion, Tiger, Crocodile, Cat, Dog, Cow, Cangaroo, Rat, Bull, Ox, Zebra] - Empty? -- false
[Lion, Tiger, Crocodile, Cat, Dog, Cow, Cangaroo, Rat, Bull, Ox] - Empty? -- false
[Kotlin, Java] - Empty? -- false
[Kotlin, Java, C] - Empty? -- false
[Kotlin, Java] - Empty? -- false
[Kotlin] - Empty? -- false
[] - Empty? -- true
Testing pushAll
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 1, 2, 12, 909]
Testing pop count
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 1, 2, 12, 909]
[Kotlin, Java]
[Kotlin, Java, C]
[Kotlin, Java]