C++ program to find sum of Even/Odd numbers between 1 to N

Explanation of program :
First, we declare one variable "sum" with value 0, and then we are going to use this variable to store sum of all even/odd numbers between 1 and N . Now we will ask user that whether to add even numbers or odd numbers and store this in a variable 'c'. Now after taking input (N) from the user, we will call function even_sum or odd_sum ,according to users choice entered before. Now , in that function we will declare a variable 'a' which will initially store first even/odd number, then we will continue a loop until 'a' is less than or equal to N.

C++ Program to find sum of N even/odd number

#include<bits/stdc++.h>
using namespace std; int odd_sum(int n) { int a=1; // first odd number int sum=0; while(a <= n) // loop for n numbers { sum=sum+a; a=a+2; // for next odd number } return sum; } int even_sum(int n) { int a=2; // first even number int sum=0; while(a <= n) // loop for n numbers { sum=sum+a; a=a+2; // for next odd number } return sum; } int main() { int n,sum; char c; cout<<"Enter 'E' to find sum of even numbers\n"; cout<<"or Enter 'O' to find sum of odd numbers\n"; cin>>c; cout<<"Enter n\n"; cin>>n; if(c=='E' || c=='e') { sum=even_sum(n); } else { sum = odd_sum(n); } cout<<sum<<"\n"; return 0; }