JuniorTheoryCommon

What does the program print?

SWIFT

func sum(_ n: Int) -> Int {
    if n == 1 {
        return 1
    }
    return n + sum(n - 1)
}
print(sum(4))

Expecting 4: thinking all the calls share one n. Each call gets its own copy of n, so sum(4) still adds 4 after sum(3) returns.
Expecting 1: thinking the base case's value goes straight to print. sum(1) returns to sum(2), and each call on the way back adds its own n.

JuniorTheoryCommon

SWIFT

func sum(_ n: Int) -> Int {
    if n == 1 {
        return 1
    }
    return n + sum(n - 1)
}
print(sum(4))

Expecting 4: thinking all the calls share one n. Each call gets its own copy of n, so sum(4) still adds 4 after sum(3) returns.
Expecting 1: thinking the base case's value goes straight to print. sum(1) returns to sum(2), and each call on the way back adds its own n.