[20250925] BOJ / G5 / 숫자고르기 / 이준희

JHLEE325/202509/25 BOJ G5 숫자고르기.md

@@ -0,0 +1,44 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    static int n;
+    static int[] arr;
+    static boolean[] visited;
+    static Set<Integer> result = new TreeSet<>();
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st;
+        StringBuilder sb = new StringBuilder();
+
+        n = Integer.parseInt(br.readLine());
+
+        arr = new int[n +1];
+        for (int i = 1; i <= n; i++) {
+            arr[i] = Integer.parseInt(br.readLine());
+        }
+
+        for (int i = 1; i <= n; i++) {
+            visited = new boolean[n +1];
+            dfs(i, i);
+        }
+
+        sb.append(result.size()).append("\n");
+        for (int x : result) sb.append(x).append("\n");
+        System.out.print(sb);
+    }
+
+    static void dfs(int start, int cur) {
+        if (!visited[cur]) {
+            visited[cur] = true;
+            dfs(start, arr[cur]);
+        } else {
+            if (cur == start) {
+                result.add(cur);
+            }
+        }
+    }
+}
+```