for loop adding numbers c++ code example

Example 1: c++ sum of all numbers up to a number

// Method 1: Mathematical -> Sum up numbers from 1 to n 
int sum(int n){
	return (n * (n+1)) / 2;
}

// Method 2: Using a for-loop -> Sum up numbers from 1 to n 
int sum(int n){
	int tempSum = 0; 
  	for (int i = n; i > 0; i--){
     	tempSum += i;  
    }
  	return tempSum; 
}

// Method 3: Using recursion -> Sum up numbers from 1 to n 
int sum(int n){
	return n > 0 ? n + sum(n-1) : 0; 
}

Example 2: how to add numbers in for loop c++

#include <iostream>

int main() {
  int n = 0;
  int sum = 0;
  std::cout << "Please enter and integer: ";
  std::cin >> n;

  //this will ensure that the integer is posetive.
  while (n < 0 ) {
    std::cout <<"Please enter positive integer only.\n";
    std::cout << "Please enter and integer: ";
    std::cin >> n;
  }

  for (int i = 0; i < n ; i++) {
    std::cout << i << "\n";
    sum +=i
  }
  std::cout << "Sum of odd numbers is " << sum <<".\n";

}