C++ function does not execute in the main section - c++

Question

I am having difficulties with a program that does not execute a function and i cant seem to find the problem.
This little piece of code that I'm trying to write should ask the user to enter the size of the 2d array and after that search each row and calculate the average of the rows.
It executes just fine until the calculation results come up.
The example:
Enter the size of the array: 2
2
Enter the element of the 1 row and 1 column: 10
Enter the element of the 1 row and 2 column: 20
Enter the element of the 2 row and 1 column: 50
Enter the element of the 2 row and 2 column: 20
Program ended with exit code: 0
and code of the program:
#include <iostream>
#include <iomanip>
using namespace std;
void calculate(int n, int m, int matrix[10][10], double sum, double avg[10], int k); //to calculate the average of each row
void input(int n, int m, int matrix[10][10]); //to input the requirements
void results(double avg[10],int n); //to output the results
int main() {
int matrix[10][10]; //the array
int n,m; //rows and columns entered by the user
double avg[10]; //average of the array rows, which will be calculated later
int k; //number of positive elements
double sum; //to calculate sum
input(n, m, matrix);
calculate(n, m, matrix, sum, avg, k);
results(avg, n);
return 0;
}
void input(int n, int m, int matrix[10][10]) {
cout<<"Enter the size of the array: ";
cin>>n>>m; //the real elements of the array
for (int i=0; i<n; i++) {
for (int j=0; j<m; j++) {
cout<<"Enter the element of the "<<i+1<<" row and "<<j+1<<" column: "; //entering each element of the array
cin>>matrix[i][j];
}
}
}
void calculate(int n, int m, int matrix[10][10], double sum, double avg[10], int k) {
for (int i=0; i<n; i++) {
k=0;
sum=0;
avg=0;
for (int j=0; j<m; j++) {
if (matrix[i][j]>0) {
sum+=static_cast<double>(matrix[i][j]);
k++;
}
}
if (k>0) {
avg[i]=sum/static_cast<double>(k);
}
}
}
void results(double avg[10], int n) {
for (int i=0; i<n; i++) { //
cout<<"Average of "<<i<<" row is equal to: "<<avg[i]<<"\n";
}
}

Answer 1

There are multiple problems with your code:
You ask the user for the size of your array, but you have the array defined with constant size:
int matrix[10][10];
What would happen if user entered 11? It would result in an undefined behavior. Consider using std::vector if you want to have truly dynamic arrays.
When you read your n, m values inside void input(int n, int m, int matrix[10][10]) procedure, you are making changes to the copies of those variables (i.e. they are passed by value), so, the changes are only visible to the inside of the function. When you leave the scope of that function, all changes you did to them, are lost. You need to pass those parameters by reference, i.e.:
void input(int& n, int& m, int matrix[10][10]);
That way, the compiler won't do a copy, and you will be changing the same variables from your main.
Having that in mind, you would need to change your calculate procedure in a similar way:
void calculate(int n, int m, int matrix[10][10], double& sum, double avg[10], int& k);
No need for variables n, and m to be passed by reference, since, in this case, they are input parameters, and don't need to be changed.

Answer 2

You are not changing n and m in main(). input() takes in the parameters by value which mean it makes a copy so the changes done in the function are local only to the function. To fix this just pass n and m by reference.
void input(int& n, int& m, int matrix[10][10])