[백준] 10814번 나이순 정렬 문제! (silver 5

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.StringTokenizer;
public class Main{
	public static void main(String[] args) throws IOException {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		BufferedWriter bw=new BufferedWriter(new OutputStreamWriter(System.out));
		StringTokenizer st;
		int n=Integer.parseInt(br.readLine());
		ArrayList<String>[] people=new ArrayList[100001];
		for(int i=0; i<n; i++) {
			st=new StringTokenizer(br.readLine());
			int age=Integer.parseInt(st.nextToken());
			if(people[age]==null) {
				people[age]=new ArrayList<>();
				people[age].add(st.nextToken());
			}
			else {
				people[age].add(st.nextToken());
			}
		}
		
		for(int i=0; i<people.length; i++) {
			if(people[i]==null) {
				continue;
			}
			for(int j=0; j<people[i].size(); j++) {
				bw.write(i+" "+people[i].get(j)+"\n");
			}
		}
		bw.flush();
		bw.close();
	}
}