[백준2438] 별 찍기 -1

https://www.acmicpc.net/problem/2438

2438번: 별 찍기 - 1

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방법1. 이중 for문만 사용하기

package step3;

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Day08_2438 {

	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int N = Integer.parseInt(br.readLine());
		br.close();
		for (int s = 1; s <= N; s++) {
			for (int j = 1; j <= s; j++) {
				System.out.print("*");
			}
			System.out.println(" ");
		}

	}

}

방법2. StringBuilder 사용하기

package step3;

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Day08_2438_2 { //use to StringBuilder

	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int N = Integer.parseInt(br.readLine());
		br.close();

		StringBuilder sb = new StringBuilder();

		for (int s = 1; s <= N; s++) {
			for (int j = 1; j <= s; j++) {
				sb.append("*");
			}
			sb.append("\n");
		}

		System.out.print(sb);
	}

}

StringBuilder사용으로  System.out.print()호출을 줄이니, 시간이 훨씬 단축된 것을 확인할 수 있다.