Question

How to sum of all the prime numbers in an array with C#

Answer 1

using System;

class Program
{
    static bool isPrime(int n) {
            if (n == 0) return false;
            if (n == 1) return false;
            for (int i = 2; i <= (int)Math.Sqrt(n); i++) {
                if (n % i == 0)
                    return false;
            }
            return true;
    }
    static void Main() {
        int[] arr = new int[] {4, 8, 5, 17, 9, 22, 21, 13, 18, 99};
        int sum = 0;

        for (int i = 0; i < arr.Length; i++) {
            if (isPrime(arr[i])) {
                sum += arr[i]; // 5 17 13
            }
        }
        Console.WriteLine(sum);
    }
}



/*
run:

35

*/

 

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