力扣-12.28-650

方法一：
参考：https://leetcode-cn.com/problems/2-keys-keyboard/solution/zhi-you-liang-ge-jian-de-jian-pan-by-leetcode/
理解为分解素数

class Solution {
    public int minSteps(int n) {
        int ans = 0, d = 2;
        while (n > 1) {
            while (n % d == 0) {
                ans += d;
                n /= d;
            }
            d++;
        }
        return ans;
    }
}

方法二：
递归

class Solution {
    public int minSteps(int n) {
        if (n == 1) {
            return 0;
        }
        for (int i = 2; i <= Math.sqrt(n); i++) {
            if (n % i == 0) {
                return i + minSteps(n / i);
            }
        }
        return n;
    }
}

转化为动态规划

class Solution {
    public int minSteps(int n) {
        int[] dp = new int[n + 1];
        dp[1] = 0;
        int h = (int)Math.sqrt(n);
        for (int i = 2; i <= n; i++) {
            dp[i] = i;
            for(int j = 2; j <= h; j++) {
                if(i % j == 0) {
                    dp[i] = dp[j] + dp[i / j];
                    break;
                }
            }
        }
        return dp[n];
    }
}

这题不明白！！！