给定数字乘积的最小数字

/*
 * Leetcode Problem 2847: Smallest Number With Given Product
 * 
 * Problem Statement:
 * Given an integer n, return the smallest positive integer that has a digit product of n.
 * If no such integer exists, return -1.
 * 
 * Approach:
 * 1. If n is less than 10, return n (since the smallest number with the digit product n is n itself).
 * 2. Use a list to store the digits.
 * 3. Iterate from 9 down to 2 and for each digit, add it to the list if it divides n.
 * 4. Sort the list and convert it to a number.
 */

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class SmallestNumberWithProductStream {
    public static int smallestNumber(int n) {
        if (n < 10) return n;
        List<Integer> digits = new ArrayList<>();
        for (int i = 9; i >= 2; i--) {
            while (n % i == 0) {
                digits.add(i);
                n /= i;
            }
        }
        if (n > 1) return -1;
        Collections.sort(digits);
        return digits.stream().reduce(0, (a, b) -> a * 10 + b);
    }

    public static void main(String[] args) {
        System.out.println(smallestNumber(36)); // Output: 49
        System.out.println(smallestNumber(100)); // Output: 455
        System.out.println(smallestNumber(7)); // Output: 7
    }
}