Collect positive floats & output the average when negative integer is input - c++

Question

I'm trying to write a program that reads in positive float numbers from the user and then when the user's is a negative number, gives the average of the numbers, excluding the negative.
#include <iostream>
using namespace std;
int main() {
float av_number, total = 0, input;
do {
for (int i = 1; i >= 1; i = ++i) {
cout << "Please input a number: ";
cin >> input;
total = total += input;
av_number = total / i;
cout << av_number << endl;
break;
}
} while (input >= 0);
cout << av_number << endl;
}
When I run this, the program simply adds the inputs together on each line, and then subtracts my final negative input before closing the program.
If I were to guess, It's likely a logical confliction within my sequence of do & for loops, but I'm unable to identify the issue. I may have also misused i in some fashion, but I'm not certain precisely how.
Any help would be appreciated as I'm still learning, Cheers!

Answer 1

you don't need the for loop, you just need some iterator to count the number of entered numbers, so you can delete that for loop and use a counter variable instead.
also, you are breaking in the loop without checking if the input < 0, so you can write this
if (input < 0)
break;
also, you shouldn't calculate av_number = total / counter; except only after the end of the big while loop
it's total += input; not total = total += input;
writing while (input >= 0) wouldn't make sense as long as you are breaking inside the loop when input < 0, so you can write while (true); instead
and this is the code edited:
#include <iostream>
using namespace std;
int main() {
float av_number = 1.0, total = 1, input = 1.0;
int counter = 0;
do {
cout << "Please input a number: ";
cin >> input;
if (input < 0)
break;
counter++;
total += input;
} while (true);
av_number = total / counter;
cout << av_number << endl;
}
and this is the output:
Please input a number: 5
Please input a number: 12
Please input a number: 7
Please input a number: -2
8
P.S : read more about Why is "using namespace std;" considered bad practice?

Answer 2

You should move the calculation of the average value out of the loop where the adding takes place and only add non-negative values to total.
#include <iostream>
int main() {
float total = 0.f;
int i = 0;
// loop for as long as the user successfully enters a non-negative value:
for (float input; std::cout << "Please input a number: " &&
std::cin >> input &&
!(input < 0.f); ++i)
{
// now `input` is non-negative
total += input; // and only sum it up here, no average calculation
}
if (i > 0) { // avoid division by zero
// finally calculate the average:
float av_number = total / i;
std::cout << av_number << '\n';
}
}
The condition for the loop is that std::cout << "Please input a number: " succeeds and that std::cin >> input succeeds and that input is not less than zero.