https://programmers.co.kr/learn/courses/30/lessons/12930

string solution(string s) {
    string answer = s;
    int cnt = 2;
    
    for(int i = 0; i < answer.size(); i++){
        if(!isspace(s[i])){
            if(cnt % 2 == 0){
                answer[i] = toupper(answer[i]);
            }else{
                answer[i] = tolower(answer[i]);
            }
            cnt++;
        }else{
            cnt = 2;
        }
    }
    return answer;
}