refactor: change packages (#5430)

* refactor: change package

* refactor: fix name

---------

Co-authored-by: alxkm <alx@alx.com>

src/main/java/com/thealgorithms/maths/EulersFunction.java

@@ -0,0 +1,47 @@
+package com.thealgorithms.maths;
+
+/**
+ * Utility class for computing
+ * <a href="https://en.wikipedia.org/wiki/Euler%27s_totient_function">Euler's totient function</a>.
+ */
+public final class EulersFunction {
+    private EulersFunction() {
+    }
+
+    /**
+     * Validates that the input is a positive integer.
+     *
+     * @param n the input number to validate
+     * @throws IllegalArgumentException if {@code n} is non-positive
+     */
+    private static void checkInput(int n) {
+        if (n <= 0) {
+            throw new IllegalArgumentException("n must be positive.");
+        }
+    }
+
+    /**
+     * Computes the value of Euler's totient function for a given input.
+     * This function has a time complexity of O(sqrt(n)).
+     *
+     * @param n the input number
+     * @return the value of Euler's totient function for the given input
+     * @throws IllegalArgumentException if {@code n} is non-positive
+     */
+    public static int getEuler(int n) {
+        checkInput(n);
+        int result = n;
+        for (int i = 2; i * i <= n; i++) {
+            if (n % i == 0) {
+                while (n % i == 0) {
+                    n /= i;
+                }
+                result -= result / i;
+            }
+        }
+        if (n > 1) {
+            result -= result / n;
+        }
+        return result;
+    }
+}