백준 - 단계별로 풀어보기 - JAVA (12단계 : 브루트 포스 / 5문제) (2023.1.1 일)

1단계 : 2798번 / 블랙잭

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
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()); // 카드 개수
        int M = Integer.parseInt(st.nextToken()); // 카드 최대 합

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

        int result = search(arr, N, M);
        bw.write(result+"\n");
        bw.flush();
        bw.close();
    }


    static int search (int[] a, int n, int m){
        int result = 0;

        for(int i=0; i<n-2; i++){
            for(int j=i+1; j<n-1; j++){
                for(int k=j+1; k<n; k++){
                    int sum = a[i] + a[j] + a[k];

                    if (m == sum){
                        return sum;
                    }

                    if (result < sum && sum < m){
                        result = sum;
                    }
                }
            }
        }
        return result;
    } 


} // Main

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2단계 : 2231번 / 분해합

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

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));
        
        int N = Integer.parseInt(br.readLine()); 
        int result = 0;
        for (int i=1; i<N; i++){
            if (num(i) == N){
                result = i;
                break;
            }
        }

        bw.write(result+" ");
        bw.flush();
        bw.close();
    }


    static int num (int N){
        int sum = N;
        sum += N % 10;

        while (N / 10 != 0){
            N = N / 10;
            sum += N % 10;
        }

        return sum;
    } 


} // Main

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3단계 : 7568번 / 덩치

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
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));
        
        int N = Integer.parseInt(br.readLine()); 
        int[][] person = new int[N][2];

        StringTokenizer st;
        for(int i=0; i<N; i++){
            st = new StringTokenizer(br.readLine());
            person[i][0] = Integer.parseInt(st.nextToken());
            person[i][1] = Integer.parseInt(st.nextToken());
        }


        StringBuilder sb = new StringBuilder();

        for(int i=0; i<N; i++){
            int rank = 1;

            for(int j=0; j<N; j++){
                if (i == j){
                    continue;
                }

                if (person[i][0] < person[j][0] && person[i][1] < person[j][1]){
                    rank ++;
                }
            }

            sb.append(rank).append(" ");
        }
        bw.write(sb.toString());
        bw.flush();
    }
} // Main

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4단계 : 1018번 / 체스판 다시 칠하기

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.StringTokenizer;

public class Main{

    public static boolean[][] arr; // W : true, B : false
    public static int min = 64;

    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()); // 가로 길이
        int M  = Integer.parseInt(st.nextToken()); // 세로 길이
        
        arr = new boolean[N][M]; // 타일 색상 판단 배열 생성

        for(int i=0; i<N; i++){
            String str = br.readLine();

            for(int j=0; j<M; j++){
                if (str.charAt(j) == 'W'){
                    arr[i][j] = true;
                }
                else {
                    arr[i][j] = false;
                }
            }
        } // 타일 저장 완료!

        int N_row = N - 7;
        int M_column = M - 7;

        for(int i=0; i<N_row; i++){
            for(int j=0; j<M_column; j++){
                find(i, j);
            }
        }

        bw.write(min+" ");
        bw.flush();
        bw.close();
    }

    public static void find(int x, int y) { // (x, y) : 자를 타일의 맨왼쪽 상단 좌표
        // (end_x, end_y) : 맨 오른쪽 하단 좌표
        int end_x = x + 8; 
        int end_y = y + 8;
        
        int count = 0;

        boolean TF = arr[x][y]; // 첫번쨰 칸의 색

        for(int i=x; i<end_x; i++){
            for(int j=y; j<end_y; j++){

                if (arr[i][j] != TF){
                    count ++;
                }

                TF = (!TF); // 인접한 칸의 색은 서로 다른색.
            }
            TF = (!TF); // 줄 갱신시 다른 색.
        }

        count = Math.min(count, 64 - count); // 첫 타일 'W' or 'B' 비교.

        min = Math.min(min, count); // 최솟값 (min) 갱신.
    }

} // Main

* boolean 2차원 배열을 통해 타일 색 판단하기

* 8X8 크기의 타일을 자르는 경우 (N-7) * (M-7)

* 자른 타일의 시작하는 색 : 'B', 'W'

Math.min(a, b); // 두 수 중 작은 값을 return

[참고 문서]

 

https://st-lab.tistory.com/101

[백준] 1018번 : 체스판 다시 칠하기 - JAVA [자바]

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5단계 : 1436번 / 영화감독 숌

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

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));
        
        int N  = Integer.parseInt(br.readLine()); // N번째 영화

        int i=666; int count_N=0; int result = 0;
        while(true){
            if (check(i)) {
                count_N ++;
                if(count_N == N){
                    result = i;
                    break;
                }
            }
            i++;
        }

        bw.write(result+" ");
        bw.flush(); bw.close();
        
    }

    // 종말 숫자 판단 함수
    public static boolean check(int num){
        while (true){
            if (num % 1000 == 666){break;}
            if (num / 10 == 0){break;}
            num = num / 10;
        }
        if (num % 1000 == 666) {return true;}
        else {return false;}
    }

} // Main

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