[백준 20438] 출석체크 (JAVA)

https://www.acmicpc.net/problem/20438

20438번: 출석체크

 

실버2 레벨에 맞지 않게..

아주 간단하게 구간을 확인하여 풀 수 있는 문제였다. 

 

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.HashMap;
import java.util.Map;
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 = new StringTokenizer(br.readLine());
		int N = Integer.parseInt(st.nextToken());
		int K = Integer.parseInt(st.nextToken());
		int Q = Integer.parseInt(st.nextToken());
		int M = Integer.parseInt(st.nextToken());

		int[] arr = new int[N + 3];
		// 졸고 있는 학생 - 2
		// 출첵한 학생 - 1
		// 아무것도 안한 학생 - 0
		st = new StringTokenizer(br.readLine());
		for (int i = 0; i < K; i++) {
			int idx = Integer.parseInt(st.nextToken());
			arr[idx] = 2;
		}

		st = new StringTokenizer(br.readLine());
		for (int i = 0; i < Q; i++) {
			int idx = Integer.parseInt(st.nextToken());
			int n = 1;
			if (arr[idx] != 2) {
				for (int idx2 = idx; idx2 < N + 3; idx2 += idx) {
					if (arr[idx2] != 2)
						arr[idx2] = 1;
					n++;
				}
			}
		}

		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < M; i++) {
			st = new StringTokenizer(br.readLine());
			int start = Integer.parseInt(st.nextToken());
			int end = Integer.parseInt(st.nextToken());
			int count = 0;
			for (int j = start; j <= end; j++) {
				if (arr[j] == 0 || arr[j] == 2)
					count++;
			}
			sb.append(count).append("\n");
		}

		bw.write(sb.toString());
		bw.flush();
		bw.close();
		br.close();
	}

}