백준[JAVA] 10816.숫자 카드 2 - 자바

📖 문제

📃 코드

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));
        StringBuilder sb = new StringBuilder();

        int N = Integer.parseInt(br.readLine());
        int[] card = new int[N];

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

        int M = Integer.parseInt(br.readLine());
        st = new StringTokenizer(br.readLine(), " ");
        for (int i = 0; i < M; i++) {
            int key = Integer.parseInt(st.nextToken());

            sb.append(upperBound(card, key) - lowerBound(card, key)).append(' ');
        }
        System.out.println(sb);
    }

    private static int lowerBound(int[] card, int key) {
        int lo = 0;
        int hi = card.length;

        // loop when lo = hi
        while (lo < hi) {
            int mid = (lo + hi) / 2;
            // if key(second input number) is repetition or lower
            // -> search lower index for length of repitition
            if (key <= card[mid]) {
                hi = mid;
            } else {
                lo = mid + 1;
            }
        }
        return lo;
    }

    private static int upperBound(int[] card, int key) {
        int lo = 0;
        int hi = card.length;

        // loop when lo = hi
        while (lo < hi) {
            int mid = (lo + hi) / 2;
            // if key(second input number) is lower than mid
            // -> search lower index for upperBound
            if(key < card[mid]){
                hi = mid;
            }else{
                // repitition number is +1 index for search upperBound
                lo = mid + 1;
            }
        }
        return lo;
    }
}

 

🔗 링크

https://www.acmicpc.net/problem/10816

10816번: 숫자 카드 2