Question

How to write a function that gets n and returns the sum: 1+ 2 + 3 +...+ n in C++

Answer 1

#include <iostream>

int sum(int n);

int main() {
    int n;

    std::cout << "Enter a number: ";
    std::cin >> n;
    
    int result = sum(n);

    std::cout << "\nsum = " << result << std::endl;
}

int sum(int n) {
    int sum = 0;

    for (int i = 1; i <= n; i++) {
        std::cout << i; // for testing - can be deleted
        if (i < n) std::cout << " + "; // for testing - can be deleted
        sum += i;
    }

    return sum;
}


/*
run:

Enter a number: 5
1 + 2 + 3 + 4 + 5
sum = 15

*/

 

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