JuniorTheoryCommon

What does the program print?

JAVA

public class Main {
    static int f(int n) {
        return n == 0 ? 0 : n + f(n - 1);
    }
    public static void main(String[] args) {
        System.out.println(f(4));
    }
}

Expecting 0: the base case's 0 goes back to f(1), not to main; each waiting call adds its own n, so the answers grow to 1, 3, 6 and 10.
Expecting a StackOverflowError: n reaches 0, and the ?: returns 0 there without another call, so the chain stops after five calls.

What happens if the program calls f(-1)?
How would you compute the same sum with a loop?

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JuniorTheoryCommon

What does the program print?

JAVA

public class Main {
    static int f(int n) {
        return n == 0 ? 0 : n + f(n - 1);
    }
    public static void main(String[] args) {
        System.out.println(f(4));
    }
}

Expecting 0: the base case's 0 goes back to f(1), not to main; each waiting call adds its own n, so the answers grow to 1, 3, 6 and 10.
Expecting a StackOverflowError: n reaches 0, and the ?: returns 0 there without another call, so the chain stops after five calls.

What happens if the program calls f(-1)?
How would you compute the same sum with a loop?

Back to questions Open topic in roadmap →Answer it yourself — Quiz