New 병아리 개발자

# 2438 별 찍기

• 숫자 입력받아 별 찍기

import java.io.*;

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 num = Integer.parseInt(br.readLine());

    for ( int i = 1; i <= num; i++ ) {
      for ( int k = 1; k <= i; k++ ) {
        bw.write("*"); 
      }
      bw.write("\n");
    }

    bw.flush();
    bw.close();

  }
}

# 2439 별 찍기

• 숫자 입력받아 별 찍기

import java.io.*;

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 num = Integer.parseInt(br.readLine());

    for ( int i = 1; i <= num; i++ ) {
      for ( int k = num; k >= 1; k-- ) {
        if ( k <= i ) {
          bw.write("*");     
        } else {
          bw.write(" ");     
        }
        
      }
      bw.write("\n");
    }

    bw.flush();
    bw.close();

  }
}

# 2741 N 찍기 자바

• Scanner 보다 BufferedReader, BufferedWriter를 사용하는게 효율적이다.

import java.io.*;

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 num = Integer.parseInt(br.readLine());

    for ( int i = 1; i <= num; i++ ) {
      bw.write((i) + "\n");
    }

    bw.flush();
    bw.close();

  }
}

# 백준 15552 빠른 A+B 자바

• BufferedReader, BufferedWriter 이용

import java.io.*;

class Main {
  public static void main(String[] args) throws IOException {

    BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
    BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

    int num = Integer.parseInt(bf.readLine());

    for ( int i = 0; i < num; i++ ) {
      String temp = bf.readLine();
      String[] arr = temp.split(" ");
      int a = Integer.parseInt(arr[0]);
      int b = Integer.parseInt(arr[1]);
      bw.write((a+b) + "\n");
    }
    
    bw.flush();
    bw.close();

  }
}

# 자바 알람 시계 문제

• 입력된 시간 보다 45분 전 울리는 알람 시계 문제

import java.util.Scanner;

public class Main {
  public static void main(String[] args) {

    Scanner scanner = new Scanner(System.in);

    int h = scanner.nextInt();
    int m = scanner.nextInt();

    m = (m - 45);

    if ( m < 0 ) {
      if ( h == 0 ) {
        h = 24 - 1;
      } else {
        h = h - 1;
      }
      m = 60 + m;
    }

    System.out.println(h + " " + m);

  }
}