how to count the number of "numbers in for" - c++

Question

everyone, I build a programme to know even and odd number from given numbers.
The even and odd number works just fine, and i want to know the total count of numbers ranging from the start number to the end number but it always says 11 at the output for both.
How do I solve this? and is there any function to count letters/numbers because it will be very helpful.
I did search it up but I can't find any Thank you
#include<stdio.h>
#include <iostream>
using namespace std;
int main(){
int number;
int firstNum,secondNum;
int countOdd,countEven;
cout << "Enter the first number: ";
cin >> firstNum;
cout << "Enter the second number: ";
cin >> secondNum;
if (firstNum>secondNum )
cout << "Sorry the first number must be less than second number";
else
cout << "Odd numbers in given range are: ";
for(number = firstNum;number <= secondNum; number++)
if(number % 2 !=0)
cout << number<< " ";
countOdd = number;
cout << "\nTotal count of odd number is :" << countOdd << endl;
printf("\nEven numbers in given range are: ");
for(number = firstNum;number <= secondNum; number++)
if(number % 2 ==0)
cout << number << " ";
countEven = number;
cout << "\nTotal count of even number is :" << countEven << endl;
return 0;
}

Answer 1

Code to count odd and even numbers:
using namespace std;
// Return the number of odd numbers
// in the range [L, R]
int countOdd(int L, int R){
int N = (R - L) / 2;
// if either R or L is odd
if (R % 2 != 0 || L % 2 != 0)
N += 1;
return N;
}
// Driver code
int main()
{
int L = 3, R = 7;
int odds = countOdd(L, R);
int evens = (R - L + 1) - odds;
cout << "Count of odd numbers is " << odds << endl;
cout << "Count of even numbers is " << evens << endl;
return 0;
}

Answer 2

You are overwriting your counts with every iteration of the for loop. countOdd = number; should be moved inside the if statement and read more like this:
if (number % 2 != 0) {
cout << number << " ";
countOdd++;
}
That way you will actually be counting the numbers as you find them.
This goes the same for the code in the counting of even numbers.
if (number % 2 == 0) {
cout << number << " ";
countEven++;
}
And don't forget to initialize the counters variables before using them:
countOdd = countEven = 0;