알고리즘 - 백준, 2445 별 찍기 -8

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

public class Main{
    public static void main(String[] args)throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb1 = new StringBuilder();
        StringBuilder sb2 = new StringBuilder();
        
        int value = Integer.parseInt(br.readLine());
        int length = value*2 -1;
        
        for(int i=1; i<=length; i++){
             if(i<=value){
                 for(int j=1; j<=i; j++){
                     sb1.append("*");
                 }
                 for(int k=1; k<=value-i; k++){
                     sb1.append(" ");
                 }
                 
             } else if(i> value){
                 for(int j=1; j<= (2*value-i) ; j++){
                     sb1.append("*");
                 }
                 for(int k=1; k<=-(value-i); k++ ){
                     sb1.append(" ");
                 }
             }
            sb2.append(sb1.toString()).append(sb1.reverse().toString()).append("\n");
            sb1.delete(0, sb1.length());
        }
        
        String result = sb2.toString();
        
        System.out.print(sb2);
    }
}