백준_12891_DNA비밀번호

https://www.acmicpc.net/problem/12891

처음 풀이

import java.io.*;
import java.util.*;

public class Main {
    static int S;
    static int P;
    static char[] dna;
    static int[] rule;
    static int[] now;

    static boolean check(int[] rule, int[] now) {
        for (int i = 0; i < 4; i++) {
            if (rule[i] > now[i]) return false; // 규칙 숫자에 미치지 못할 경우 실패!
        }
        return true;
    }

    public static void main(String[] args) throws IOException {
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));

        StringTokenizer st = new StringTokenizer(bf.readLine());
        S = Integer.parseInt(st.nextToken());
        P = Integer.parseInt(st.nextToken());

        dna = bf.readLine().toCharArray();

        rule = new int[4];
        st = new StringTokenizer(bf.readLine());

        for (int i = 0; i < 4; i++) {
            rule[i] = Integer.parseInt(st.nextToken());
        }

        now = new int[4];
        int ans = 0;

        // 우선 맨 처음 ~ P까지 확인
        for (int i = 0; i < P; i++) {
            if (dna[i] == 'A') now[0] += 1;
            else if (dna[i] == 'C') now[1] += 1;
            else if (dna[i] == 'G') now[2] += 1;
            else if (dna[i] == 'T') now[3] += 1;
        }

        if (check(rule, now)) ans += 1;

        // 탐색 i를 끝점으로 잡아서 탐색!
        for (int i = P; i < S; i++) {
            int start = i - P; // 탐색하며 빠지게 됨

            if (dna[start] == 'A') now[0] -= 1;
            else if (dna[start] == 'C') now[1] -= 1;
            else if (dna[start] == 'G') now[2] -= 1;
            else if (dna[start] == 'T') now[3] -= 1;

            if (dna[i] == 'A') now[0] += 1;
            else if (dna[i] == 'C') now[1] += 1;
            else if (dna[i] == 'G') now[2] += 1;
            else if (dna[i] == 'T') now[3] += 1;

            if (check(rule, now)) ans += 1;
        }

        System.out.println(ans);
    }
}

📌 1. i를 끝점으로 잡아서 탐색하기

• 탐색 조건 잘 생각하자
• start 인덱스 = i - p
• 입력을 char[] 배열로 변환 ( CCTGGATTG )

dna = bf.readLine().toCharArray();

🤔 좀더 객체 지향적으로

public class Main {
    static int S;
    static int P;
    static String str;
    static int[] rule;
    static int[] now;

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        S = Integer.parseInt(st.nextToken());
        P = Integer.parseInt(st.nextToken());

        str = br.readLine();

        rule = new int[4];
        now = new int[4];

        st = new StringTokenizer(br.readLine());
        for (int i = 0; i < 4; i++) {
            rule[i] = Integer.parseInt(st.nextToken());
        }

        int ans = 0;
        for (int i = 0; i < P; i++) {
            updateCount(str.charAt(i), 1);
        }

        if (check()) {
            ans++;
        }

        for (int i = P; i < S; i++) {
            updateCount(str.charAt(i - P), -1);
            updateCount(str.charAt(i), 1);

            if (check()) {
                ans++;
            }
        }

        System.out.println(ans);
    }

    static void updateCount(char ch, int delta) {
        if (ch == 'A') {
            now[0] += delta;
        } else if (ch == 'C') {
            now[1] += delta;
        } else if (ch == 'G') {
            now[2] += delta;
        } else if (ch == 'T') {
            now[3] += delta;
        }
    }

    static boolean check() {
        for (int i = 0; i < 4; i++) {
            if (now[i] < rule[i]) {
                return false;
            }
        }
        return true;
    }
}