Wrong values read into array from file?

[YikUTM]

This is my code

#include <iostream>
#include <fstream>
#include <string>
#include <cmath>
#include <cstdlib>
using namespace std;

//Function Prototypes
void readfile(string, string );
float sqDiff(int[], int[], int);
float sum(int[], int);
float f(int [], int, int, int);

int main()
{
	
	int size=0;
	float setA[size];
	float setB[size];
	
	string filename1; //declare first file
	string filename2;//declare second file
	
	cout<<"Enter file 1 : ";
	getline(cin,filename1); //input name for first file

	cout<<"Enter file 2 : ";
	getline(cin,filename2); //input name for second file
	
	readfile(filename1,filename2); //read file 1 & 2 into array
	
	
	return 0;
}

void readfile(string filenameA, string filenameB)
{
	ifstream indata;
	ifstream indata2;
	
	indata.open(filenameA.c_str());
	indata2.open(filenameB.c_str());
	
	int num=0;
	int num2=0;
	
	int setA[num];
	int setB[num2];
	
	
	int sqdiff;
	
        //PROBLEM START
	while(!indata.eof()) 
	{
		indata>>setA[num];
		num++;
	}
	indata.clear();
	
	while(!indata2.eof())
	{	
		indata2>>setB[num2];
		num2++;
	}
	indata2.clear();
        //PROBLEM END
	if(num==num2)
	{
		sqdiff=sqDiff(setA, setB, num);	
		
		
	}
	
	else
	{
		cout<<"** Both arrays are not of the same size. Please try again! **";
	}
}

float sqDiff(int arr1[], int arr2[], int size)
{
	int squarediff[size];
	int addition1, addition2;
	float Formula;

	int diff[size];
	
	for(int i=0; i<size; i++)
	{
		diff[i]=arr1[i]-arr2[i];

		squarediff[i]=pow(diff[i],2);
	}
   
	addition1=sum(arr1,size);
	addition2=sum(arr2,size);
	Formula=f(squarediff, addition1, addition2, size);
	cout<<endl<<endl<<"Result: f= "<<Formula;
}

float sum(int array[], int ArraySize)
{
	int s=0;
	
	for(int i=0; i<ArraySize; i++)
	{
		s+=array[i];
	}
	
	return s;
}

float f(int SQDIFF[], int SUM1, int SUM2, int SIZE)
{
	int SumSQdiff=0;
	float MeanX;
	float MeanY;
	float AbsoluteDiff;
	float F;
	
	for(int i=0; i<SIZE; i++)
	{
		SumSQdiff+=SQDIFF[i];
	}


	MeanX=static_cast<float>(SUM1)/SIZE;

	MeanY=static_cast<float>(SUM2)/SIZE;

	AbsoluteDiff=fabs(MeanX-MeanY);

	F=(sqrt(SumSQdiff))/AbsoluteDiff;
	
	return F;
}

The first txt file
3 2 2 1 4 5 5 7

The second txt file
8 8 9 4 1 2 5 0

I tried to compare the number of integers from 2 txt files. If they have the same number of integer, then proceed. Else, program will display error.

I was able to successfully compare the number of integer. However, when I attempt to store the integers of 1st txt file to array setA[num] and store the integers of 2nd txt file to array setB[num]. It shows the following problem:

**Before the line (used to read 2nd txt to setB[num] )

while(!indata2.eof())
	{	
		indata2>>setB[num2];
		num2++;
	}

SetA[num] is still correct

setA[num] :
3 2 2 1 4 5 5 7

However after the line

setA[num] unexpectedly become

1 2 5 0 4 5 5 7

Why is this happening? Can somebody please tell me what is wrong? Any help is appreciated...

[Chervil]

Variable length arrays are not allowed in standard C++. I get this compiler error (and others):

[Error] ISO C++ forbids variable length array 'setA' [-Wvla]

Also, you are trying to use arrays with a size of zero. That will lead to corruption of some other area of memory.

And as well as that, you use eof() as a loop condition. Best avoided.

Maybe try something like this - just an example, I didn't try to copy all your code.

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int readfile(string name, int data[], int n );
void print(int data[], int n );

int main()
{
    const int size  = 100;
    
    int setA[size];
    int setB[size];
    
    
    int numA = readfile("data1.txt", setA, size);
    int numB = readfile("data2.txt", setB, size);
    
        
    print(setA, numA);
    print(setB, numB);
}


int readfile(string name, int data[], int size )
{
    ifstream indata(name.c_str());

    int count =  0;
    
    while (count < size && indata >> data[count])
        count++;
        
    return count;    
}

void print(int data[], int n )
{
    cout << "Size = " << n << '\n';      
    for (int i=0; i<n; ++i)
        cout << data[i] << ' ';
    cout << "\n\n";         
    
}

Note, I used a fixed array size of 100 elements, you may change that if necessary.

A better solution would be to use vectors, which can resize as more data is added.

[Chervil]

Version using vectors:

#include <iostream>
#include <fstream>
#include <string>
#include <vector>

using namespace std;

void readfile(string name, vector<int>& data);
void print(const vector<int>& data);

int main()
{
    vector<int> setA;
    vector<int> setB;


    readfile("data1.txt", setA);
    readfile("data2.txt", setB);

    print(setA);
    print(setB);
}


void readfile(string name, vector<int>& data)
{
    ifstream indata(name.c_str());

    int n;

    while ( indata >> n )
        data.push_back(n);
}

void print(const vector<int>& data)
{
    cout << "Size = " << data.size() << '\n';
    for (int i=0; i<data.size(); ++i)
        cout << data[i] << ' ';
    cout << "\n\n";
}

[YikUTM]

But, when I compile my code using dev c++, it can be compiled.

I have to use the 2 input txt because there are part of the question.

I am new to C++, I haven't learn about vectors yet

[Chervil]

But, when I compile my code using dev c++, it can be compiled.

That's because there are non-standard extensions provided by that compiler. It's best not to depend on them because when you use a different compiler, your code will fail.

I have to use the 2 input txt because there are part of the question.

You should be able to adapt some of the code from my first example to make it fit your requirements. I just showed a basic example for you to base your own code upon.

I am new to C++, I haven't learn about vectors yet

Then consider the code sample I gave as a gentle introduction to the topic. You don't need to use them right now, but it is something worth knowing in the future.