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LeetCode Weekly Contest 625. Minimum Factorization

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Question

Given a positive integer a, find the smallest positive integer b whose multiplication of each digit equals to a.

If there is no answer or the answer is not fit in 32-bit signed integer, then return 0.

Example 1 Input:

48 Output: 68 Example 2 Input:

15 Output: 35

Explanation

很直接的解法，从9开始找因子，存起来，最后组成最小的数。

Code

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public class Solution {
    public int smallestFactorization(int a) {
        if(a == 0) return 0;
        ArrayList<Integer> list = new ArrayList<>();
        helper(a, list);
        if (list.get(0) == 0) return 0;
        int result = 0;
        for (int i=list.size()-1; i>=0; i--) {
            int digit = i;
            result += list.get(i) * Math.pow(10,digit);
            if (result >= Integer.MAX_VALUE) {
                return 0;
            }
        }
        return result;
    }
    public void helper(int a, ArrayList<Integer> list) {
        if (a <= 9) {
            list.add(a);
            return;
        }
        boolean could = false;
        for (int i = 9; i>=2; i--) {
            if (a%i == 0) {
                could = true;
                list.add(i);
                helper(a/i, list);
                break;
            }
        }
        if(!could) {
            if (list.size() <1) list.add(0);
            else list.set(0,0);
        }
    }
}