How to calculate the average?

Question

I was asked to calculate the average of marks for 10 students. First, I was able to read and retrieve the data from data.txt file which looks like this:

No. Name Test1 Test2 Test3

1 Ahmad 58 97 83

2 Dollah 78 76 70

3 Ramesh 85 75 84

4 Maimunah 87 45 74

5 Robert 74 68 97

6 Kumar 77 73 45

7 Intan 56 23 27

8 Ping 74 58 18

9 Idayu 47 98 95

10 Roslan 79 98 78

Then I have to calculate the average for each student and determine the grades.

Here are what I've done so far.

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

using namespace std;

int main()

{
    ifstream inFile1;
    string temp;
    int line=0;

    inFile1.open("data.txt");
    if(inFile1.fail())
    {
        cout << "File cannot be opened" << endl;
        exit(1);
    }

    while(getline(inFile1, temp))
    {
        line++;
    }
    inFile1.close();

    return 0;
}

This program should at least consists two prototype function: average() and grade(). This is where I got stuck.

Answer 1

You can check the answers here: find average salaries from file in c++.

Basically when you iterate through the file lines you should split the temp string into tokens you are interested in. How? An option would be to use getline with the delimeter ' ' or look into the std::noskipws stream manipulator or simply use operator>> to read from the file - depends on the details of your requirements.

If I correctly understand your case, I'd go with the operator>> to get the name of the student and then read using getline(inFile, gradesText) to read until end of line to get all grades for the current student.

Then I'd use a separate function to split the strings into a vector of grades. How to do the splitting you can check in Split a string in C++?. This way you could prepare a function like vector<int> split(const string& line, char delim = ' '). Within the implementation you should probably use std::stoi for the string-to-int conversion.

Afterwards, when you already have a proper collection you can calculate the mean from it with:

const double sum = std::accumulate(grades.begin(), grades.end(), 0.0);
const double gradesMean = sum / grades.size();