C++ compiling issue between MAC OS X and Windows

Question

Okay, I am currently taking a course in C++ and worked really hard on a recent assignment. However, when I get my grade back I get a 67 because the program will not compile. It compiles fine on my computer before I turned it in. When I see this message, I go into my program, which has not been changed and run it. The program compiles fine! No issues. I just tested it again, right after I wrote that previous sentence, and it ran fine once more.

Now I am using Xcode, on a mac, and my teacher is using Windows Visual Studio. Not sure of the version or anything like that.

The specific line of code that she is having an issue on is the following:

int mineSpots[n][m];
for (int r = 0; r < n; r++){
    for (int c = 0; c < m; c++){
        mineSpots[r][c] = 0;
    }
}

The entire code for the program is as follows: (If you prefer you may go to my github page and see the code there as well. Which is https://github.com/ravenusmc/minesweeper_helper) Again, any help on why this is compiling on xcode and not Visual Studio would be great.

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

using namespace std;

//Global Constants
const int ROWS = 100;
const int COLS = 100;

//*******************************
//Prototype Functions
//*******************************

void buildArray(ifstream &, char [][COLS], int, int, int);
void showArray(ifstream &, ofstream &, char [][COLS], int, int, int);

//******************************
//Main Function

//******************************

int main(){

//Declaring all of the variables that I will be using in the program.
ifstream inputFile;
ofstream outputFile;

char mines[ROWS][COLS];
//Variables to keep track of the number of rows and columns.
int n, m;
//variable to keep track of the number of fields
int count = 1;

//Opening the file
inputFile.open("inputdata.txt");

//Opening/creating the file to which store the information in this program.
outputFile.open("outputdata.txt");

//Checking for errors in the file.
if (inputFile.fail())
{
    cout << "Error opening data file. Progam will now close. \n\n";
    //system("pause"); //This line is for Microsoft Visual studio users.
    exit(0);
}

//This loop will read the information from the file until it is empty.
while (!inputFile.eof()){

    //These two lines will read the numerical values in each file and then they will be used as a counter
    //for the loop.
    inputFile >> n;
    inputFile >> m;

    //If the both values are zero, the program knows to break the while loop. Also, if the values are out of range then
    //the loop will break as well.
    if (n == 0 && m == 0){
        break;
    }else if (n <= 0){
        outputFile << "Sorry, the number of rows you have is less than 0!" << endl;
        break;
    }else if (m > 100){
        outputFile << "Sorry, the number of columns you have is greater than 100!" << endl;
        break;
    }

    //Calling the function to build each of the 2D arrays
    buildArray(inputFile, mines, ROWS, n, m);

    //This line is simply to display the field for each array in the txt document.
    outputFile << "Field #" << count << endl;

    //This function will build the new arrays.
    showArray(inputFile, outputFile, mines, ROWS, n, m);

    //These lines ensure that there is a space between each array.
    cout << endl;
    outputFile << endl;

    //The count is incremented each pass to keep track of the field number.
    count++;
  }


//Closing the input file.
inputFile.close();
//Closing the output file.
outputFile.close();

system("pause"); //This line is for Microsoft Visual users.

return 0;

 }//End of main function

 //******************************
 //Functions
  //******************************

 //This function will build the array from the inputdata.txt file.
 void buildArray(ifstream &file, char values[][COLS], int rows, int n, int m){
    char row;

    //This for loop goes through the document to build the array.
    for (int r = 0; r < n; r++){
        for (int c = 0; c < m; c++){
            file >> row;
            values[r][c] = row;
        }
  }
 } // End of buildArray Function

 //This function will find all the mines and then output what it finds to      the outputdata.txt file.
   void showArray(ifstream &file, ofstream &outFile, char values[][COLS], int rows, int n, int m){

//Creating an array to hold the numbers for the mines. Each position
//Will be set to 0 at the start.
int mineSpots[n][m];
for (int r = 0; r < n; r++){
    for (int c = 0; c < m; c++){
        mineSpots[r][c] = 0;
    }
}

//This for loop is what will actually find the locations of the mines. It uses a counter to go through every position around
//a spot that has an '*' and counts to determine the correct number of mines   around that location.
for (int row = 0; row < n; row++) {
    for (int col = 0; col < m; col++) {
        if (values[row][col] == '*') {
            if ((row - 1 >= 0) && (col - 1 >= 0) ){
                mineSpots[row - 1][col - 1]++;
            }
            if (row - 1 >= 0){
                mineSpots[row - 1][col]++;
            }
            if ( (col < m - 1) && (row > 0)){
                mineSpots[row - 1][col + 1]++;
            }
            if (col - 1 >= 0){
                mineSpots[row][col - 1]++;
            }
            if (!(col >= m - 1)){
                mineSpots[row][col + 1]++;
            }

            if (col - 1 >= 0){
                mineSpots[row + 1][col - 1]++;
            }
            if ((row < n - 1) && (col < m - 1)){
                mineSpots[row + 1][col + 1]++;
            }
            mineSpots[row + 1][col]++;
        }
    }
}

//This for loop displays the array.
for (int r = 0; r < n; r++){
    for (int c = 0; c < m; c++){
        if (values[r][c] == '*'){
            outFile << '*';
        }else{
            outFile << mineSpots[r][c];
            }
        }
        cout << endl;
        outFile << endl;
}
}// End of showArray Function