[20251206] BOJ / G5 / 숫자고르기 / 김민진

Author: zinnnn37

zinnnn37/202512/6 BOJ G5 숫자고르기.md

@@ -0,0 +1,68 @@
+```java
+import java.io.*;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class BJ_2668_숫자고르기 {
+
+    private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    private static final BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    private static final StringBuilder  sb = new StringBuilder();
+
+    private static int           N;
+    private static int[]         arr;
+    private static boolean[]     visited;
+    private static List<Integer> result;
+
+    public static void main(String[] args) throws IOException {
+        init();
+        sol();
+    }
+
+    private static void init() throws IOException {
+        N = Integer.parseInt(br.readLine());
+        arr = new int[N + 1];
+
+        for (int i = 1; i <= N; i++) {
+            arr[i] = Integer.parseInt(br.readLine());
+        }
+        visited = new boolean[N + 1];
+        result = new ArrayList<>();
+    }
+
+    private static void sol() throws IOException {
+        for (int i = 1; i <= N; i++) {
+            visited[i] = true;
+            dfs(i, i);
+            visited[i] = false;
+        }
+        Collections.sort(result);
+
+        sb.append(result.size()).append("\n");
+        for (int num : result) {
+            sb.append(num).append("\n");
+        }
+        bw.write(sb.toString());
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    private static void dfs(int start, int cur) {
+        int next = arr[cur];
+
+        if (next == start) {
+            result.add(start);
+            return;
+        }
+
+        if (!visited[next]) {
+            visited[next] = true;
+            dfs(start, next);
+            visited[next] = false;
+        }
+    }
+
+}
+```