Question

Write a C++ function that takes a pointer to an array of integers as a parameter and return the number of prime integers in the array. Write main() program to test the function.

Answer 1

#include <iostream>
#include <cstdlib>

using namespace std;

int count_primes(int *arr, int size) {
    int count = 0, n;
    bool is_prime;
    for (int i = 0; i < size; ++i) {
        n = arr[i];
        is_prime = n > 1;
        for (int j = 2; j < n; ++j) {
            if (n % j == 0) {
                is_prime = false;
            }
        }
        if (is_prime)
            ++count;
    }
    return count;
}

int main() {
    int size;
    cout << "Enter size of array: ";
    cin >> size;
    cout << "Enter " << size << " integers: ";
    int *arr = new int[size];
    for (int i = 0; i < size; ++i) {
        cin >> arr[i];
    }
    int count = count_primes(arr, size);
    cout << "Number of primes in array is " << count << endl;
    return 0;
}