Some 1D array functions

#include <iostream>
#define MAXN 100
using namespace std;

void input(int &number, int a[]) {
    cin >> number;
    for(int i = 0; i < number; i++) {
        cin >> a[i];
    }
}

void output(int number, int a[]) {
    for(int i = 0; i < number; i++) {
        cout << a[i] << " ";
    }
}

int sum(int number, int a[]) {
    int total = 0;
    for(int i = 0; i < number; i++) {
        total += a[i];
    }
    return total;
}

int mini(int number, int a[]) {
    int minimum = a[0];
    for(int i = 0; i < number; i++) {
        if(a[i]<minimum) minimum = a[i];
    }
    return minimum;
}

int maxi(int number, int a[]) {
    int maximum = a[0];
    for(int i = 0; i < number; i++) {
        if(a[i]>maximum) maximum = a[i];
    }
    return maximum;
}

double avg(int number, int a[]) {
    return (double) sum(number, a) / number;
}

int in_array(int x, int number, int a[]) {
    for(int i = 0; i < number; i++) {
        if(a[i]==x) return i;
    }

    return -1;
}

void print_common(int n1, int a[], int n2, int b[]) {
    for (int i = 0; i < n1; i++)
    {
        if(in_array(a[i], n2, b)!=-1) {
            cout << a[i] << " ";
        }
    }
    cout << endl;
}

void in_array_3(int n1, int a[], int n2, int b[], int n3, int c[]) {
    for(int i = 0; i < n1; i++) {
        if(in_array(a[i], n2, b)!=-1 && in_array(a[i], n3, c)!=-1 ) {
            cout << a[i] << " ";
        }
    }

    cout << endl;
}

int is_power_of_two(int x) {
    int ed = 0;
    while(x!=0) {
        ed += (x%2);
        x/=2;
    }

    if(ed==1) {
        return true;
    } else {
        return false;
    }
}

void print_powers_of_two(int n1, int a[]) {
    for (int i = 0; i < n1; i++)
    {
        if(is_power_of_two(a[i])) {
            cout << a[i] << " ";
        }
    }
    cout << endl;
}

int digit_sum(int x) {
    int sum = 0;
    while(x!=0) sum+=x%10, x/=10;

    return sum;
}

void overwrite_element_digit_sum(int n, int a[]) {
    for (int i = 0; i < n; i++)
    {
        a[i] = digit_sum(a[i]);
    }
}

void swap(int &a, int &b) {
    int helper = b;
    b = a;
    a = helper;
}

void reverse(int n, int a[]) {
    for (int i = 0, j = n-1; i <= j; i++, j--)
    {
        swap(a[i], a[j]);
    }
}

void reverse_alternative(int n, int a[]) {
    for (int i = 0; i < n/2; i++)
    {
        swap(a[i], a[n-i-1]);
    }
}

void reverse_alternative_2(int n, int a[]) {
    int j = n-1;
    for (int i = 0; i < n/2; i++)
    {
        swap(a[i], a[j]);
        j--;
    }
}

int main() {
    int n, a[MAXN], m, b[MAXN], p, c[MAXN];
    input(n, a);
//  reverse(n, a);
    output(n, a);
    //reverse_alternative(n, a);
    //output(n, a);
    //reverse_alternative_2(n, a);
    //output(n, a);

    //overwrite_element_digit_sum(n, a);

    //input(m, b);
    //input(p, c);
    //print_common(n, a, m, b);
    //in_array_3(n, a, m, b, p, c);
    /*cout << "Powers of two in a: " << endl;
    print_powers_of_two(n, a);
    cout << "Powers of two in b: " << endl;
    print_powers_of_two(m, b);
    cout << "Powers of two in c: " << endl;
    print_powers_of_two(p, c);
    */
    return 0;
}