Daily LeetCode – day0136 1781. Sum of Beauty of All Substrings

// 1781. Sum of Beauty of All Substrings
class Solution {
    public int beautySum(String s) {
        char[] charArray = s.toCharArray();
        int len = charArray.length;
        int ans = 0;
        for (int i = 0; i < len; ++i) {
            int[] frequencies = new int[123];
            int maxFrequency = 0;
            for (int j = i; j < len; ++j) {
                ++frequencies[charArray[j]];
                if (frequencies[charArray[j]] > maxFrequency) {
                    maxFrequency = frequencies[charArray[j]];
                }
                int minFrequency = len;
                for (int k = 97; k < 123; ++k) {
                    if (frequencies[k] != 0 && frequencies[k] < minFrequency) {
                        minFrequency = frequencies[k];
                    }
                }
                ans += maxFrequency - minFrequency;
            }
        }
        return ans;
    }
}

学习笔记：
这是一道中等题，当我以为解法很特殊的时候，却发现啥也不是。
就是双重循环，就是数组。太简陋了这道题目。