https://leetcode.cn/problems/check-whether-two-strings-are-almost-equivalent/submissions/

class Solution {
public:
    bool checkAlmostEquivalent(string word1, string word2) {
        int* helper=new int[128];   //开空间，下标存小写英文字母
        memset(helper, 0, sizeof(int)*128);     //空间初始化为0，便于统计

        //word1字符串负责+1
        for(const char& ch:word1)
        {
            ++helper[ch];
        }
        //word2字符串负责-1
        for(const char& ch:word2)
        {
            --helper[ch];
        }

        //遍历；是否符合题意
        bool result=true;
        for(char i='a'; i<='z'; i++)
        {
            if(!(-3<=helper[i] && helper[i]<=3))
            {
                result=false;
                break;
            }
        }

        delete[] helper;
        return result;
    }
};