Kotlin – Fibonacci Series using Recursion

Fibonacci series using Recursion in Kotlin

In this tutorial, we will learn how to generate the Fibonacci series using recursion in Kotlin.

Examples

The Fibonacci series is a sequence of numbers where each number is the sum of the two preceding ones, usually starting with 0 and 1.

Example 1: Generating Fibonacci series

In this example, we will create a recursive function that generates the Fibonacci series up to a given number of terms.

Kotlin Program

fun generateFibonacciSeries(terms: Int): List<Int> {
    val fibonacciSeries = mutableListOf<Int>()
    for (i in 0 until terms) {
        fibonacciSeries.add(fibonacci(i))
    }
    return fibonacciSeries
}

fun fibonacci(n: Int): Int {
    return if (n <= 1) {
        n
    } else {
        fibonacci(n - 1) + fibonacci(n - 2)
    }
}

fun main() {
    val numberOfTerms = 10
    val fibonacciSeries = generateFibonacciSeries(numberOfTerms)
    println("Fibonacci Series:")
    for (term in fibonacciSeries) {
        print("$term ")
    }
}

Output

Fibonacci Series:
0 1 1 2 3 5 8 13 21 34

The function generateFibonacciSeries takes an integer terms as input and returns a list containing the first terms Fibonacci numbers. It uses a For loop to iterate from 0 to terms and calls the recursive function fibonacci to calculate each Fibonacci number.

The fibonacci function is a recursive function that calculates the nth Fibonacci number. It returns the number itself if n is less than or equal to 1; otherwise, it calls itself recursively with n - 1 and n - 2 as arguments and returns the sum of the two recursive calls.

Example 2: Generating Fibonacci series up to a specific number

In this example, we will create a recursive function that generates the Fibonacci series up to a specific number.

Kotlin Program


fun generateFibonacciSeriesUpToNumber(number: Int): List<Int> {
    val fibonacciSeries = mutableListOf<Int>()
    var i = 0
    var fibonacciNumber = fibonacci(i)
    while (fibonacciNumber <= number) {
        fibonacciSeries.add(fibonacciNumber)
        i++
        fibonacciNumber = fibonacci(i)
    }
    return fibonacciSeries
}

fun fibonacci(n: Int): Int {
    return if (n <= 1) {
        n
    } else {
        fibonacci(n - 1) + fibonacci(n - 2)
    }
}

fun main() {
    val number = 50
    val fibonacciSeries = generateFibonacciSeriesUpToNumber(number)
    println("Fibonacci Series up to $number:")
    for (term in fibonacciSeries) {
        print("$term ")
    }
}

Output

Fibonacci Series up to 50:
0 1 1 2 3 5 8 13 21 34

The function generateFibonacciSeriesUpToNumber takes an integer number as input and returns a list containing the Fibonacci numbers up to and including number. It uses a While loop to iterate and add Fibonacci numbers to the list until the next number exceeds the given number. The calculation of Fibonacci numbers is done using the recursive function fibonacci as explained in Example 1.

Summary

In this Kotlin Tutorial, we learned how to generate the Fibonacci series using recursion in Kotlin. We saw two examples: one to generate the series up to a given number of terms and another to generate the series up to a specific number.

Note: Recursion is a powerful technique in programming, but it should be used with caution to prevent stack overflow for large values.