[20250812] BOJ / G5 / 숫자고르기 / 이인희

LiiNi-coder/202508/12 BOJ 숫자고르기.md

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+```java
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.StringTokenizer;
+import java.util.ArrayList;
+import java.util.Collections;
+
+public class Main {
+    private static BufferedReader br;
+    private static StringTokenizer st;
+    private static int N;
+    private static int[] arr;
+    private static boolean[] visited;
+    private static boolean[] onPath;
+    private static ArrayList<Integer> result;
+
+    public static void main(String[] args) throws IOException {
+        br = new BufferedReader(new InputStreamReader(System.in));
+        N = Integer.parseInt(br.readLine().trim());
+        arr = new int[N + 1];
+        for (int i = 1; i <= N; i++) {
+            arr[i] = Integer.parseInt(br.readLine().trim());
+        }
+        visited = new boolean[N + 1];
+        result = new ArrayList<>();
+        for (int i = 1; i <= N; i++) {
+            onPath = new boolean[N + 1];
+            dfs(i, i);
+        }
+
+        Collections.sort(result);
+        System.out.println(result.size());
+        for (int num : result) {
+            System.out.println(num);
+        }
+
+    }
+
+    private static void dfs(int start, int current) {
+        if (onPath[current]) {
+            if (current == start) {
+                result.add(start);
+            }
+            return;
+        }
+        onPath[current] = true;
+        int next = arr[current];
+        dfs(start, next);
+        onPath[current] = false;
+    }
+}
+```