[20250722] BOJ / G4 / 좋은수열 / 이인희

LiiNi-coder/202507/22 BOJ 좋은수열.md

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+```java
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+public class Main {
+	private static BufferedReader br;
+	private static int n;
+	private static StringBuilder answer;
+	private static boolean found;
+
+	public static void main(String[] args) throws IOException {
+		br = new BufferedReader(new InputStreamReader(System.in));
+		n = Integer.parseInt(br.readLine());
+		answer = new StringBuilder();
+		found = false;
+		recur(0, new StringBuilder());
+		System.out.println(answer);
+	}
+
+	private static void recur(int depth, StringBuilder sb) {
+		if (found) return;
+
+		if (depth == n) {
+			answer.append(sb);
+			found = true;
+			return;
+		}
+
+		for (int i = 1; i <= 3; i++) {
+			sb.append(i);
+			if (isGood(sb)) {
+				recur(depth + 1, sb);
+			}
+			sb.deleteCharAt(sb.length() - 1);
+		}
+	}
+
+	private static boolean isGood(StringBuilder sb) {
+		int len = sb.length();
+		for (int size = 1; size <= len / 2; size++) {
+			String left = sb.substring(len - size * 2, len - size);
+			String right = sb.substring(len - size, len);
+			if (left.equals(right)) {
+				return false;
+			}
+		}
+		return true;
+	}
+}
+```