백준 1620번

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;

// Press Shift twice to open the Search Everywhere dialog and type show whitespaces,
// then press Enter. You can now see whitespace characters in your code.
public class Main {
public static void main(String[] args) throws IOException {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringBuilder sb = new StringBuilder();


    StringTokenizer st = new StringTokenizer(br.readLine());
    int x = Integer.parseInt(st.nextToken());
    int y = Integer.parseInt(st.nextToken());


    String[] names = new String[x+1];
    Map<String,Integer> map = new HashMap<>();

    for (int i = 1; i <= x; i++) {
        names[i] = br.readLine();
        map.put(names[i],i);
    }

    for (int i = 0; i < y; i++) {
        String line = br.readLine();
        if(map.containsKey(line))
        {
            System.out.println(map.get(line));
        }
        else{
            Integer K = Integer.parseInt(line);
            System.out.println(names[K]);
        }
    }







}

} map에서 key를 통해서 value를 구할때랑, value를 이용해서 key를 구할때는 key를 애초에 배열로 설정해놓고 구하면 쉽게 구할 수 있다.