44] 프로그래머스 완주하지 못한 선수

정렬 먼저하고 

한명만 완주를 못했으니까

 두 벡터가 다른 곳의 위치의 벡터값을 반환해주면 된다,

#include <string>
#include <vector>
#include<algorithm>
using namespace std;

string solution(vector<string> participant, vector<string> completion) {
    string answer = "";
    sort(participant.begin(), participant.end());
    sort(completion.begin(), completion.end());
    
    for(int i = 0;i<completion.size();i++)
        if(completion[i] !=  participant[i]){
           answer = participant[i];
            break;
        }
    
    if(answer =="")
        answer = participant[participant.size()-1];
                
    return answer;
}

or

#include <string>
#include <vector>
#include<algorithm>
using namespace std;

string solution(vector<string> participant, vector<string> completion) {
    string answer = "";
    sort(participant.begin(), participant.end());
    sort(completion.begin(), completion.end());
    
    for(int i = 0;i<participant.size();i++)
        if(completion[i] !=  participant[i]){
               answer = participant[i];
            break;
        }
    
    return answer;
}