[20260219] BOJ / G5 / 신기한 소수 / 이인희

Author: LiiNi-coder

LiiNi-coder/202602/19 BOJ 신기한 소수.md

@@ -0,0 +1,47 @@
+```java
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+public class Main {
+	static int N;
+	public static void main(String[] args) throws IOException {
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		N = Integer.parseInt(br.readLine());
+		//1자리 소수로 모두 시작
+		startTo(1, 2, N);
+		startTo(1, 3, N);
+		startTo(1, 5, N);
+		startTo(1, 7, N);
+	}
+
+	private static void startTo(int depth, int value, int n) {
+		if (!isPrime(value)) {
+			return;
+		}
+		if (depth == n) {
+			System.out.println(value);
+			return;
+		}
+		
+		
+		for (int digit = 1; digit <= 9; digit++) {
+			int next = value * 10 + digit;
+			startTo(depth + 1, next, n);
+		}
+	}
+
+	private static boolean isPrime(int num) {
+		if (num < 2) {
+			return false;
+		}
+		for (int i = 2; i * i <= num; i++) {
+			if (num % i == 0) {
+				return false;
+			}
+		}
+		return true;
+	}
+}
+
+```