C++ primer exercise 1.19, first attempt at the "if" statement - c++

Question

In an earlier exercise i wrote a program that took two inputs and printed out the numbers between the two numbers. in exercise 1.19, i am asked to rewrite the program so that it can handle the issue of the first number being smaller than the second number. i am asking 2 questions:
i feel as though i played a dirty trick with the if statement that
just switches the numbers around in the correct order. is that bad
coding?
what i wrote works, it "handles" the issue of the user inputting a
number that is smaller than the second. however since i am very new to
programming and only in chapter 1 of C++ primer. am i missing
something important here that would cause me to write the code
"better" (EX: if i understood X concept then i would wrote the "if"
statement better/differently)
int main()
{
int v1 = 0, v2 = 0, e1 = 0, e2 = 0, sum = 0;
std::cout << "Input first integer: ";
std::cin >> v1; std::cout << std::endl;
e1 = v1;
std::cout << "Input secound integer: ";
std::cin >> v2; std::cout << std:: endl;
if (v1 > v2)
{
e1 = v1;
e2 = v2;
v1 = e2;
v2 = e1;
e1 = v1;
}
while (v1 <= v2)
{
sum += v1;
++v1;
}
std::cout << "The inclusive sum of " << e1 << " and " << v2 << " is "
<< sum;
return 0;
}

Answer 1

To answer your second question (and indirectly your first) I recommend that you use the swap function from the C++ Standard Library. You can check it out here. In general, using STL code is better than writing functions yourself (for obvious reasons).
So to implement it in your code, you'll need to first:
#include <algorithm>
Then in the body of that first if statement, just say:
std::swap(v1, v2);

Answer 2

You can use only a single extra variable, and simplify your if considerably.
int v1 = 0, v2 = 0, sum = 0;
std::cout << "Input first integer: ";
std::cin >> v1; std::cout << std::endl;
std::cout << "Input secound integer: ";
std::cin >> v2; std::cout << std:: endl;
if (v1 > v2)
{
int tmp = v1; // Store v1 in a temp variable
v1 = v2; // Move v2's value into v1
v2 = tmp; // Move temp variable into v2
}

Answer 3

What I did for this is used an if else
int main()
{
int val1 = 0, val2 = 0, sum = 0;
std::cout << "Enter in 2 numbers " << std::endl;
std::cin >> val1;
std::cin >> val2;
// if the first value is smaller than the second then do below
if(val1<val2)
{
sum = val1; // setting sum equal to the first value entered
while(val1<=val2) // run while val1 is less than or equal to val2
{
std::cout << sum << std::endl; // printing sum
sum++; // adding +1 to sum
val1++; // adding +1 to val1 otherwise it will print sum to infinity
}
}
else // If the second value is smaller than the first entered do below
{
sum = val2; // setting sum equal to the second value entered
while(val2<=val1)
{
std::cout << sum << std::endl;
sum++; // adding +1 to sum
val2++; // adding +1 to val2 otherwise it will print sum to infinity
}
}
std::cout << "woot!" << std::endl;
return 0;
}
It gets rid of the swapping. Took me a little while to get it. I didn't think I needed to add the val1++ or val2++ so it was just printing out numbers as fast as possible. Cool to look at, but not what I wanted. Hope this helps somebody!
Note: Mine is a little different from what the problem is asking for. Adding a set of numbers together but I believe the same logic can be used.