Recursive Functions

In this lesson you will learn how to write a recursive function in Kotlin and understand how a function can call itself. This is for anyone searching for "Kotlin recursive function how to use".

A recursive function is a function that calls itself. It suits work that repeats the same calculation pattern, such as "n! = n x (n-1)!".

The sample code has factorial call itself as n * factorial(n - 1) to compute the factorial of 5. The stopping condition if (n <= 1) return 1 is what makes the chain of calls come to an end.

A common stumbling block for beginners is forgetting that stopping condition. Without one, the function calls itself forever and the program crashes.

In real-world development, deep recursion consumes a lot of stack, so it is worth considering whether a loop would do instead.

📖 Reference code

fun factorial(n: Int): Int {
    if (n <= 1) return 1
    return n * factorial(n - 1)
}
fun main() {
    println(factorial(5))
}

✍️ Your code

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🧪 This site can't compile or run Kotlin directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).