C++(코딩테스트) - 오픈채팅방

#include <string>
#include <vector>
#include <map>

using namespace std;

vector<string> solution(vector<string> record) {
	vector<string> answer;


	map<string, string> id;

	for (int i = 0; i < record.size(); i++)
	{
		string a[3];
		int k = 0;
		for (int j = 0; j < record[i].size(); j++)
		{
			if (record[i][j] != ' ')
			{
				a[k].push_back(record[i][j]);
			}
			else
			{
				k++;
			}
		}
		if (a[0] == "Enter" || a[0] == "Change")
		{
			id.erase(a[1]);
			id[a[1]] = a[2];
		}
	}
	for (int i = 0; i < record.size(); i++)
	{
		string a[3];
		int k = 0;
		for (int j = 0; j < record[i].size(); j++)
		{
			if (record[i][j] != ' ')
			{
				a[k].push_back(record[i][j]);
			}
			else
			{
				k++;
			}
		}
		if (a[0] == "Enter")
		{
			answer.push_back(id[a[1]] + "님이 들어왔습니다.");
		}
		if (a[0] == "Leave")
		{
			answer.push_back(id[a[1]] + "님이 나갔습니다.");
		}
	}
	return answer;
}