Implemented overall functionality for yesterdays practice exercise

1 files changed, 35 insertions, 0 deletions

diff --git a/Year 1/Object-oriented Programming/07-Practice-05.04.2022/NumberHelpers.cpp b/Year 1/Object-oriented Programming/07-Practice-05.04.2022/NumberHelpers.cpp
new file mode 100644
index 0000000..d7843b4
--- /dev/null
+++ b/Year 1/Object-oriented Programming/07-Practice-05.04.2022/NumberHelpers.cpp
@@ -0,0 +1,35 @@
+#include "NumberHelpers.h"
+
+bool isEven(int x) {
+	return x % 2 == 0;
+}
+
+// The following functions are taken from my own Interval task solution
+
+bool isPowerOfTwo(int x)
+{
+	return x > 0 &&            // No (normal) power of 2 creates negatives or 0
+		   (x & (x - 1)) == 0; // Thanks https://stackoverflow.com/a/600306/12036073, original implementation was a lot less efficient
+}
+
+bool isPrime(int num) // Forked from my own implementation - https://gitlab.com/Syndamia/algorithms/-/blob/master/C/IsPrime.c
+{
+	if (num < 0) num *= -1; // This is required, since we calculate sqrt(num)
+
+	if (num == 2 || num == 3 || num == 5 || num == 7 || num == 11 || num == 13)
+		return true;
+
+	// A lot of numbers are divisible by these ones, so we're going to do a bit of simple optimization
+	if (num == 0 || num == 1 || num % 2 == 0 || num % 3 == 0 || num % 5 == 0 || num % 7 == 0 || num % 11 == 0 || num % 13 == 0)
+		return false;
+
+	// All primes follow the formula 6n +- 1 (where n >= 1). Since we've already checked up to 13, we're going to
+	// start with 18 - 1 = 17. Also using root of number to eliminate a lot of checks.
+	// Primary source: https://en.wikipedia.org/wiki/Primality_test#Simple_methods
+	for (int i = 18, root = sqrt(num); i - 1 <= root; i += 6)
+	{
+		if (num % (num - 1) == 0 || num % (num + 1) == 0)
+			return false;
+	}
+	return true;
+}