완주하지 못한 선수

#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(); ){
        string n_part = participant[i];
        string n_comp = completion[i];
        if(n_part == n_comp) i++;
        else return n_part;
    }
    return participant.back();
}