grade report array outfile

#include <iostream>
#include <string>
#include <limits>
#include <cmath>
#include <iomanip>
#include <fstream>

using namespace std;

int testScoreArray[100];
void selectSort(int testScoreArray[], int n);
void fileOutput(int testScoreArray[]);

int main()

{
    int n = 100;

    ifstream infile;
    infile.open("testscoresarrayhomework.txt");

    for (int i = 0; i < 100; i++) {

        infile >> testScoreArray[i];
    }

    selectSort(testScoreArray, n);
    fileOutput(testScoreArray);

    infile.close();

    return 0;
}

void selectSort(int testScoreArray[], int n)
{
    int pos_max, temp;

    for (int i = 0; i < n - 1; i++) {
        pos_max = i;

        for (int j = i + 1; j < n; j++) {

            if (testScoreArray[j] > testScoreArray[pos_max])
                pos_max = j;
        }

        if (pos_max != i) {
            temp = testScoreArray[i];
            testScoreArray[i] = testScoreArray[pos_max];
            testScoreArray[pos_max] = temp;
        }
    }
};

void fileOutput(int testScoreArray[])
{

    ofstream outfile;
    int gradeEvent = 1;
    int previousGrade = 0;

    outfile.open("testscoresoutput.txt");
    outfile << "Test Score Breakdown: ";
    outfile << endl
            << "Score / Occurance";

    for (int i = 0; i < 100; i++) {

        if (previousGrade == testScoreArray[i]){
            gradeEvent++;
        }

        if (previousGrade && previousGrade != testScoreArray[i]) {

            outfile << '\n' << previousGrade << " / " << gradeEvent;
            gradeEvent=1;
        }


        previousGrade = testScoreArray[i];
    }
                outfile << '\n' << previousGrade << " / " << gradeEvent;


    outfile.close();
};