File isn't being read? (C++)

Question

I am attempting to read numbers from a text file into a program, but for some reason, the program isn't reading the file. Here is my code:

#include <iostream>
#include <stream>
using namespace std; 

int main()
{

ifstream infile; 

infile.open ("adventDay1.txt"); 

if (!infile) { //Check if file is opening 

    cerr << "Error!"<< endl;

    return 0; 
}

int dataSize = 0;
infile >> dataSize; 
int* arr; 
arr = new int[dataSize]; //dynamically allocated array

int measureCount = 0; //Keep track of input from file 


for (int i = 0; i < dataSize; i++) {

   // infile >> dataSize; 

    arr[i] = dataSize;

    measureCount += 1; 
}

 cout << measureCount << endl; 

delete[] arr; //Delete dynamically allocated memory 
return 0; 
}

Each time I run it, it just displays the "Error." message I added, There are 2,000 numbers in the text file. so that should be the expected output based on what I have here. I can't pinpoint the mistake.

Answer 1

Include fstream and ensure that you are opening the file in read mode. Perhaps also define it as ifstream infile("adventDay1.txt")