Added Prime Solutions

1 files changed, 96 insertions, 0 deletions

diff --git a/pract_SI/Pract. 04/Solutions/task14.cpp b/pract_SI/Pract. 04/Solutions/task14.cpp
new file mode 100644
index 0000000..c95c36c
--- /dev/null
+++ b/pract_SI/Pract. 04/Solutions/task14.cpp
@@ -0,0 +1,96 @@
+#include <iostream>
+#include <cmath>
+
+using namespace std;
+
+//Function to check whether a number is prime
+bool isPrime(int number)
+{
+	int size = sqrt(number);
+	                         
+
+	for (int i = 2; i <= size; i++)
+	{
+		if (number % i == 0)
+			return false;
+	}
+
+	return true;
+}
+
+//Print all prime numbers that are smaller than N
+void printAllPrimeToNumber(int number) //Interval [1 ; N]
+{
+	std::cout << "1" << ", 2";
+
+	for (int i = 3; i <= number; i += 2)
+	{
+		if (isPrime(i))
+			std::cout << ", " << i;
+	}
+
+	std::cout << "." << std::endl;
+}
+
+//PrimeFactorization 
+void PrimeFactor(int number)
+{
+	for (int i = 2; i <= number; i++)
+	{
+		if (isPrime(i) && number % i == 0)
+		{
+			if (i == number) //last step, no space
+				std::cout << i;
+			else
+				std::cout << i << " ";
+
+			number /= i;
+			i--;
+		}
+	}
+	std::cout << std::endl;
+}
+
+//Function whether the number N can be expressed as a sum of two prime numbers
+bool checkSumOfTwoPrimes(int number,int &primeOfNumber)
+{
+	int size = number / 2; //36 = 7 + 29, 16 = 3 + 13 , 36 = 5 + 31
+	for (int i = 2;i <= size; i++)
+	{
+		//16 = 3 + x , x = 16 - 3 , x = 13 PRIME
+		if (isPrime(i) && isPrime(number - i))
+		{
+			primeOfNumber = i;
+			return true; 
+		}
+	}
+	return false;
+}
+
+int main()
+{
+	int number;
+	std::cin >> number;
+
+	if (isPrime(number))
+		std::cout << number << " is prime!" << std::endl;
+	else
+		std::cout << number << " is composite number!" << std::endl;
+
+	std::cout << std::endl << "Prime numbers up to " << number << " are: ";
+	printAllPrimeToNumber(number);
+
+	std::cout << "Factoring of: " << number << " is: ";
+	PrimeFactor(number);
+
+	int primeOfNumber;
+	if (checkSumOfTwoPrimes(number, primeOfNumber))
+		std::cout << primeOfNumber << " + " << number - primeOfNumber << std::endl;
+	else
+		std::cout << "Error!" << std::endl;
+
+  
+
+
+	return 0;
+}