백준 2445번 : 별 찍기 - 8

import java.io.*;

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));
        StringBuilder sb = new StringBuilder();
        int n = Integer.parseInt(br.readLine());
        for (int i = 0; i < n * 2-1; i++){
            int len = i >= n ? n*2-1 - i : i + 1;
            int len2 = i >= n ? i + 1 : n*2-1-i;
            for (int j = 0; j < n * 2; j++){
                if (j < len || j >= len2) {
                    sb.append("*");
                } else {
                    sb.append(" ");
                }
            }
            sb.append("\n");
        }
        bw.write(sb.toString());
        bw.flush();
        bw.close();
    }
}