/* A howling prime is a prime number if the sum of its digits is also a prime number. For Example: Input:113 Output: true (113 is a prime number, 1+1+3=5 is also a prime number) Input: 89 Output: true (89 is a prime number, 8+9=17 is also a prime number) Input: 19 Output: false (19 is a prime number, but 1+9=10 is not a prime number) Write a program to check if the user input is a howling prime or not. BONUS: Print all the howling prime numbers in a given range. */ #include #include using namespace std; bool isHowling(size_t number); bool isPrime(const size_t& number); int main() { size_t range_begin; size_t range_end; // range of the numbers to be checked cin >> range_begin >> range_end; //if first number in range greater than second //just swap them if(range_begin > range_end) { swap(range_begin, range_end); } cout << "All howling primes in: " << range_begin << " - " << range_end << endl << endl; for(size_t i = range_begin; i <= range_end; ++i) { if(!isPrime(i)) { continue; } if(isHowling(i)) { cout << i << " - is howling prime"; } else { cout << i << " - is not howling prime"; } cout << endl; } return 0; } bool isHowling(size_t number) { size_t sum = 0; while(number) { sum += number % 10; number /= 10; } return isPrime(sum); } bool isPrime(const size_t& number) { if(number == 2) { return true; } //even number cannot be prime else if(number % 2 == 0) { return false; } for(size_t i = 2; i < number / 2; ++i) { if(number % i == 0) { return false; } } return true; }

[Assignment] Howling Prime