why it write the last twice??

[sadi]

good day all;

I have a question says

Write a complete C++ program that keeps read numbers from user (i.e. while(cin)), then find and write on a file each number with its divisors. At the end of the file write the number that has the maximum sum of divisors with its index.

Example:

input:
Enter Number 1: 25
Enter Number 2: 20
Enter Number 3: 5
Enter Number 4: 12
Enter Number 5: ^z (ctrl + z)

output file:
25: 5
20: 2 4 5 10
5: no divisors
12: 2 3 4 6
20 has maximum sum of divisors with index 2

here the code,

#include <iostream>
#include <fstream>

using namespace std;

int main ()
{
	int num, factor = 2,
		factSum = 0, index = 0,
		maxSum = 0, maxIndex = 0, maxNum;

	int count = -1;
	
	ofstream outFile;
	outFile.open("num.txt");

	while (cin)
	{
		cout << "Enter number " << index + 1 << ": ";
		cin >> num;	

		index ++;						//count the number we read
	
		outFile << num << " : ";

		//find factors and it's sum
		while (factor <= (num/2))
		{
			if (num % factor == 0)
			{
				outFile << factor;
				if (factor < (num/2))		//I won't comma after the last number but ...
					outFile << ", ";
				factSum += factor;
			}
			factor ++;
		}

		if (factSum == 0)
			outFile << "There is no divisors.";

		//find the number with max sum of factors
		if (factSum > maxSum)
		{
			maxSum = factSum;			//need for the condition
			maxIndex = index;			//need to print it
			maxNum = num;				//need to print it
		}
		
		//initialize the value
		outFile << endl;
		factSum = 0;
		factor = 2;

	}

	//print the result
	outFile << maxNum << " has the maximum sum of divisors with index " << maxIndex;
	outFile.close();

	return 0;
}

now the problem is that the output repeat the last number twice !! for example
instead of the result appear like befor, it appear like this

output file:
25: 5
20: 2 4 5 10
5: no divisors
12: 2 3 4 6
12: 2 3 4 6
20 has maximum sum of divisors with index 2

the cause as I think is when I enter (ctrl+z) to stop reading, the program use the last value it has and calculate it divisors.

now how can I solve this problem, and let the compiler read the last value once not twice???

and thanks alot for your help.

regards

[jsmith]

You have to check the input stream after line 20.

if( cin ) {
  // then do stuff
}

[sadi]

I use if (cin)
but nothing change!!

does I use it in wrong way??
I use it after while(cin) directly

thanks

[z05DSL3A]

#include <iostream>
#include <fstream>

using namespace std;

int main ()
{
    int num, factor = 2,
        factSum = 0, index = 0,
        maxSum = 0, maxIndex = 0, maxNum;

    int count = -1;
    
    ofstream outFile;
    outFile.open("num.txt");

    while (cin)
    {
        cout << "Enter number " << index + 1 << ": ";
        if( cin >> num)  
        {

            index ++;                        //count the number we read
    
            outFile << num << " : ";

            //find factors and it's sum
            while (factor <= (num/2))
            {
                if (num % factor == 0)
                {
                    outFile << factor;
                    if (factor < (num/2))        //I won't comma after the last number but ...
                        outFile << ", ";
                    factSum += factor;
                }
                factor ++;
            }

            if (factSum == 0)
                outFile << "There is no divisors.";

            //find the number with max sum of factors
            if (factSum > maxSum)
            {
                maxSum = factSum;            //need for the condition
                maxIndex = index;            //need to print it
                maxNum = num;                //need to print it
            }
            
            //initialize the value
            outFile << endl;
            factSum = 0;
            factor = 2;
        }

    }

    //print the result
    outFile << maxNum << " has the maximum sum of divisors with index " << maxIndex;
    outFile.close();

    return 0;
}

[sadi]

Oh, thanks