Getting the Average,Min, and Max of numbers in 2D array - c++

Question

I have a problem with getting the min,max, and average of an elements of 2D array.
I have a 2D array which contains Students and Grades.
I am generating the grades with rand. For example When I enter 2,2 it prints me out
Courses : 01 02 Average Min Max
ID
01 8 50 29
02 74 59 29
, My average function takes the first ones average and doesnt take the others average.
Here is my code ;
int A[30][30];
int findAverage(int noOfStudents ,int noOfGrades ){
float sum,average;
for (int i = 0 ; i < noOfGrades ; i++) {
for (int j = 0; j<noOfStudents; j++) {
sum += A[i][j];
}
average = sum / noOfGrades;
// cout << " " << format(average);
sum = 0;
return format(average);
}
and here how I use it
int main() {
int noOfCourses , noOfStudents;
cin >> noOfCourses >> noOfStudents;
cout << "Courses : " ;
for (int i = 0; i < noOfCourses; i++) {
if (i+1 >= 10) {
cout << i+1 << " ";
}else{
cout <<"0" << i+1 << " ";
}
}
cout << "Average Min Max";
for(int i=0; i<noOfStudents; i++) { //This loops on the rows.
for(int j=0; j<noOfCourses; j++) { //This loops on the columns
A[i][j] = genGrade();
}
}
cout << "\n ID " << endl;
for(int i=0; i<noOfStudents; i++) { //This loops on the rows.
if (i+1 >= 10) {
cout <<" " << i+1 << " ";
}else{
cout <<" 0" << i+1 << " ";
}
//cout <<" 0" << i+1 << " ";
for(int j=0; j<noOfCourses; j++) { //This loops on the columns
if (A[i][j] >= 10 && A[i][j] <=99) {
cout <<" " << A[i][j] << " ";
}
if(A[i][j] < 10) {
cout <<" " << A[i][j] << " ";
}
if (A[i][j] == 100) {
cout << A[i][j] << " ";
}
}
cout <<" "<<findAverage(noOfStudents,noOfCourses);
cout << endl;
}
}
What am I doing wrong ? Also How could I get the min,max of the per array?

Answer 1

I would strong recommend using containers for this task. For example you could do the following
typedef std::vector<float> grades;
std::vector<grades> student_grades;
//populate
for(const grades& gr : student_grades) {
float min, max, avg;
std::tie(min, max)=std::minmax(gr.begin(), gr.end());
avg=std::accumulate(gr.begin(), gr.end(), 0.0) / gr.size());
std::cout << "Min" << min << " Max: " << max << " Avg: " << avg << std::endl;
}
http://en.cppreference.com/w/cpp/algorithm/minmax
http://en.cppreference.com/w/cpp/algorithm/accumulate
http://en.cppreference.com/w/cpp/utility/tuple/tie

Answer 2

For starters, you are returning from inside your loop:
for (int i = 0 ; i < noOfGrades ; i++) {
for (int j = 0; j<noOfStudents; j++) {
...
}
...
return ...;
}
Can you see how the outer loop will only ever execute once?

Answer 3

The problem is that in your findAverage function you have a return statement within the loop that is looping through the rows. If you want a very simple fix add another parameter to the findAverage function that indicates which row to calculate the average for.
int findAverage(int course ,int noOfGrades ){
float sum,average;
for (int j = 0; j<noOfStudents; j++) {
sum += A[course][j];
}
average = sum / noOfGrades;
return format(average);
}
and call it like this
cout <<" "<<findAverage(i,noOfCourses);