29.小D的‘abc’变换问题

#include <iostream>
#include <string>
using namespace std;

string operator_string(string s){
    string res = {};
    for(auto c: s){
        if(c == 'a'){
            res.append("bc");
        }else if (c == 'b'){
            res.append("ca");
        }else{
            res.append("ab");
        }
    }
    return res;
}
string solution(string s, int k) {
    // PLEASE DO NOT MODIFY THE FUNCTION SIGNATURE
    // write code here
    for(int i = 0; i < k; i++){
        s = operator_string(s);
    }
    return s;
}

int main() {
    cout << (solution("abc", 2) == "caababbcbcca") << endl;
    cout << (solution("abca", 3) == "abbcbccabccacaabcaababbcabbcbcca") << endl;
    cout << (solution("cba", 1) == "abcabc") << endl;
    return 0;
}

简单不解释