Question

Write a C++ program that asks the user to enter a single number from 1 to 50 and a choice of "even" or "odd". Using a recursive function, output the sum of all the even or odd integers from 1 up to (and including) that number. Your program does not need to loop and accept more input (only one input of the number then even/odd).

Answer 1

#include <iostream>

using namespace std;

int sum(int n, bool even) {
    if (n <= 0) {
        return 0;
    } else {
        int total = sum(n - 1, even);
        if (n % 2 == 0 && even) {
            total += n;
        } else if (n % 2 == 1 && !even) {
            total += n;
        }
        return total;
    }
}

int main() {
    int n, choice;
    cout << "Enter a number between 1 and 50: ";
    cin >> n;

    cout << "1. Sum odd numbers\n2. Sum even numbers\nEnter your choice: ";
    cin >> choice;

    cout << "Sum is " << sum(n, choice==2) << endl;
    return 0;
}