Reads a file called grades.txt with a list of grades, one on each line, and outputs the average of all the numbers, as well as the lowest and highest score. Uses vectors to account for an unlimited number of grades.

calcGrades-vector.cpp

#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

double findAvg(vector<double>);
double min_max(vector<double>, bool);

int main() {
    vector<double> grades;
    
    ifstream in;
    in.open("grades.txt");
    int currLine;
    while (in >> currLine) grades.push_back(currLine);
    in.close();
    
    cout << "Average of grades: " << findAvg(grades) << endl;
    cout << "Lowest score: " << min_max(grades, false) << endl;
    cout << "Highest score: " << min_max(grades, true) << endl;
}

double findAvg(vector<double> grades) {
    double sum = 0;
    double avg = 0;
    for (int i = 0; i < grades.size(); i++) sum+=grades.at(i);
    avg = double(sum) / double(grades.size());
    return avg;
}

double min_max(vector<double> grades, bool max = false) {
    double val = grades.at(0);
    for (int i = 0; i < grades.size(); i++) if ((max && (val < grades.at(i))) || (val > grades.at(i))) val = grades.at(i);
    return val;
}