Taco - pierwszy temat

#include <iostream>
#include <cstdlib>

//program z 1 tematu jakby ktos pytal

using namespace std;

bool generate_array_of_random_numbers(int* &arr, int n, int a, int b);
void show_array(int* arr, int n);
bool check_if_nondescending(int *arr, int n);
int find_max_el(int *arr, int n);
int sum_array(int *arr, int n);
int mean_array(int *arr, int n);

int main()
{
    int n, a, b, start, max_step;
    int *arr=nullptr;
    cout << "podaj rozmiar tablicy" << endl;
    cin >> n;
    cout << "podaj poczatek przedzialu" << endl;
    cin >> a;
    cout << "podaj koniec przedzialu" << endl;
    cin >> b;

    if(generate_array_of_random_numbers( arr, n, a, b)==1){
            show_array( arr, n);
            cout << "" << endl;
    }
    else {
        cout << " niepoprawna tablica " << endl;
    }

    cout<< "max element to: "<< find_max_el(arr, n)<< endl;
    cout<< "suma wynosi: "<< sum_array(arr, n) << endl;
    cout << "srednia wynosi: " << mean_array(arr, n)<< endl;

    return 0;
}
bool generate_array_of_random_numbers(int* &arr, int n, int a, int b){
    if(arr == nullptr){
    arr = new int[n];
int diff = b-a+1;
for( int i = 0; i<n; i++)
    arr[i]=a+rand()%diff;
return true;}
    else{
return false;
    }
}


void show_array(int* arr, int n){
for(int i=0; i<n; i++)
    cout << arr[i] << " ";
}

bool check_if_nondescending(int *arr, int n){
if(arr == nullptr and n == 0)
    return true;
for(int i=0; i<n; i++)
    if(arr[i]>arr[i+1])
    return false;
return true;
}

int find_max_el(int *arr, int n){
if(arr == nullptr or n == 0)
    return -1;
int maxel = arr[0];
for (int i =0; i<n; i++)
if(arr[i]> maxel){
    maxel= arr[i];
}
return maxel;
}

int sum_array(int *arr, int n){
int suma = 0;
if( arr != nullptr){
            for(int i = 0; i<n; i++)
        suma=suma+arr[i];}
else{
 suma = 0;
}
return suma;
}

int mean_array(int *arr, int n){
int z;
int srednia;
if( arr != nullptr){
z = sum_array(arr, n);
srednia = z/n;}
else{
    srednia = 0;
}
return srednia;
}