使用质因数之和替换后可以取到的最小值

/*
 * Problem: Given a positive integer n, replace n with the sum of its prime factors,
 * repeating this process until n cannot be replaced anymore.
 * Return the smallest value that n can be.
 *
 * Approach:
 * 1. Create a helper function to find the prime factors of a number using streams.
 * 2. Replace n with the sum of its prime factors and repeat until n cannot be reduced further.
 * 3. Return the final value of n.
 */
import java.util.stream.IntStream;

public class Solution {
    public int smallestValue(int n) {
        while (true) {
            int sumOfPrimeFactors = sumPrimeFactors(n);
            if (sumOfPrimeFactors == n) break;
            n = sumOfPrimeFactors;
        }
        return n;
    }

    private int sumPrimeFactors(int n) {
        int sum = 0;
        for (int i = 2; i * i <= n; i++) {
            while (n % i == 0) {
                sum += i;
                n /= i;
            }
        }
        if (n > 1) sum += n;
        return sum;
    }

    public static void main(String[] args) {
        Solution sol = new Solution();
        System.out.println(sol.smallestValue(15)); // Output: 5
        System.out.println(sol.smallestValue(3));  // Output: 3
    }
}