[백준/자바] 1920 - 수 찾기

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashSet;
import java.util.Set;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        Set<String> set = new HashSet<>();

        int n = Integer.parseInt(br.readLine());
        String[] arr1 = br.readLine().split(" ");

        for(String s : arr1) set.add(s);

        int m = Integer.parseInt(br.readLine());
        String[] arr2 = br.readLine().split(" ");

        for(String s : arr2){
            if(set.contains(s)) System.out.println(1);
            else System.out.println("0");
        }

        br.close();
    }
}

---

이진 탐색을 이용한 풀이 (Arrays.sort() 때문인지 시간 초과가 났다.)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int N = Integer.parseInt(br.readLine());

        int[] arr = new int[N];
        StringTokenizer st = new StringTokenizer(br.readLine());
        for (int i = 0; i < N; i++) {
            arr[i] = Integer.parseInt(st.nextToken());
        }

        Arrays.sort(arr);

        int M = Integer.parseInt(br.readLine());
        st = new StringTokenizer(br.readLine());

        for (int i = 0; i < M; i++) {
            boolean found = false;
            int target = Integer.parseInt(st.nextToken());

            int start = 0;
            int end = arr.length - 1;

            while (start <= end) {
                int midIndex = (start + end) / 2;
                int midValue = arr[midIndex];

                if (midValue > target)
                    end = midIndex;
                else if (midValue < target)
                    start = midIndex + 1;
                else {
                    found = true;
                    break;
                }
            }

            if (found) System.out.println(1);
            else System.out.println(0);
        }
    }
}