[Programmers]핸드폰 번호 가리기

https://school.programmers.co.kr/learn/courses/30/lessons/12948

#include <string>
#include <vector>

using namespace std;

string solution(string phone_number) {
    string answer = "";
    
    for(int i = 0; i<phone_number.size()-4; i++){
        answer.push_back(42);
    }
    
    for(int i = phone_number.size()-4; i<phone_number.size(); i++){
        answer.push_back(phone_number[i]);
    }
    
    return answer;
}