I can give you some tips and hints to get you started.
So first, I would get the value from file, store it as a string, and check if first character (the first number) is the digit you're looking for or not.
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ifstream inputFile;
inputFile.open("data.txt");
string number;
int counter1; // this value will hold the count for the values whose first digit is 1
inputFile >> number; // get the number from file and store its value into string number
while (!inputFile.eof()) // loop until the end of file
if (number[0] == "1") // if first digit of number (index 0) equals 1, increment counter1
{
counter1 += 1;
}
Now what you need to do, is do the same if-else thing to check if first digit equals 2,3,4 etc...
Hint: You'll need to use an another loop (probably a for-loop) to do that