Solution 1

Python3

class Solution:
    def smallestFactorization(self, num: int) -> int:
        if num < 2:
            return num
        ans, mul = 0, 1
        for i in range(9, 1, -1):
            while num % i == 0:
                num //= i
                ans = mul * i + ans
                mul *= 10
        return ans if num < 2 and ans <= 2**31 - 1 else 0

Java

class Solution {
    public int smallestFactorization(int num) {
        if (num < 2) {
            return num;
        }
        long ans = 0, mul = 1;
        for (int i = 9; i >= 2; --i) {
            if (num % i == 0) {
                while (num % i == 0) {
                    num /= i;
                    ans = mul * i + ans;
                    mul *= 10;
                }
            }
        }
        return num < 2 && ans <= Integer.MAX_VALUE ? (int) ans : 0;
    }
}

C++

class Solution {
public:
    int smallestFactorization(int num) {
        if (num < 2) {
            return num;
        }
        long long ans = 0, mul = 1;
        for (int i = 9; i >= 2; --i) {
            if (num % i == 0) {
                while (num % i == 0) {
                    num /= i;
                    ans = mul * i + ans;
                    mul *= 10;
                }
            }
        }
        return num < 2 && ans <= INT_MAX ? ans : 0;
    }
};

Go

func smallestFactorization(num int) int {
    if num < 2 {
        return num
    }
    ans, mul := 0, 1
    for i := 9; i >= 2; i-- {
        if num%i == 0 {
            for num%i == 0 {
                num /= i
                ans = mul*i + ans
                mul *= 10
            }
        }
    }
    if num < 2 && ans <= math.MaxInt32 {
        return ans
    }
    return 0
}

Problem