Artemis: Refactor Primes Class for Enhanced Efficiency and Clarity

app/src/main/java/algorithms/Primes.java

@@ -1,6 +1,7 @@
 package algorithms;
+import java.util.ArrayList;
 
-import java.util.Vector;
+import java.util.ArrayList;
 
 public class Primes {
  /**
@@ -13,8 +14,14 @@ public static boolean IsPrime(int n) {
  if (n < 2) {
  return false;
  }
- for (int i = 2; i < n; i++) {
- if (n % i == 0 && i != n) {
+ if (n == 2) {
+ return true;
+ }
+ if (n % 2 == 0) {
+ return false;
+ }
+ for (int i = 3; i * i <= n; i += 2) {
+ if (n % i == 0) {
  return false;
  }
  }
@@ -29,9 +36,9 @@ public static boolean IsPrime(int n) {
  */
  public static int SumPrimes(int n) {
  int sum = 0;
- for (int i = 0; i < n; i++) {
+ for (int i = 2; i < n; i++) {
  if (IsPrime(i)) {
- sum = sum + i;
+ sum += i;
  }
  }
  return sum;
@@ -41,16 +48,20 @@ public static int SumPrimes(int n) {
  * Finds all primes factors of a number
  *
  * @param n The number to find the prime factors of.
- * @return An vector of all prime factors of n.
+ * @return An ArrayList of all prime factors of n.
  */
- public static Vector<Integer> PrimeFactors(int n) {
- Vector<Integer> ret = new Vector<Integer>();
+ public static ArrayList<Integer> PrimeFactors(int n) {
+ ArrayList<Integer> ret = new ArrayList<>();
 
- for (int i = 2; i < n; i++) {
- if (n % i == 0 && IsPrime(i)) {
+ for (int i = 2; i * i <= n; i++) {
+ while (n % i == 0) {
  ret.add(i);
+ n /= i;
  }
  }
+ if (n > 1) {
+ ret.add(n);
+ }
  return ret;
  }
-}
+}