JuniorTheoryCommon

What does the program print?

KOTLIN

fun sumTo(n: Int): Int {
    if (n == 0) return 0
    return n + sumTo(n - 1)
}

fun main() {
    println(sumTo(4))
}

Expecting 0: thinking return 0 in the base case ends everything. It answers only sumTo(0); each waiting call then adds its own n on the way back.
Expecting 24: reading the function as a product of the numbers. It adds with + and returns 0 at 0, so the result is 4 + 3 + 2 + 1 + 0.

JuniorTheoryCommon

KOTLIN

fun sumTo(n: Int): Int {
    if (n == 0) return 0
    return n + sumTo(n - 1)
}

fun main() {
    println(sumTo(4))
}

Expecting 0: thinking return 0 in the base case ends everything. It answers only sumTo(0); each waiting call then adds its own n on the way back.
Expecting 24: reading the function as a product of the numbers. It adds with + and returns 0 at 0, so the result is 4 + 3 + 2 + 1 + 0.