[20250920] BOJ / G3 / 텀 프로젝트 / 이인희

LiiNi-coder/202509/20 BOJ 텀 프로젝트.md

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+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    static int n;
+    static int[] arr;
+    static boolean[] visited;
+    static int answer = 0;
+    static int[] indegree;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        int t = Integer.parseInt(br.readLine());
+        while(t-- > 0){
+            n = Integer.parseInt(br.readLine());
+            arr = new int[n + 1];
+            visited = new boolean[n + 1];
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            for (int i = 1; i <= n; i++) {
+                arr[i] = Integer.parseInt(st.nextToken());
+            }
+
+            for (int i = 1; i <= n; i++) {
+                if (!visited[i]) {
+                    dfs(i);
+                }
+            }
+
+            System.out.println(n - answer);
+        }
+
+    }
+
+    static void dfs(int start) {
+        Map<Integer, Integer> map = new HashMap<>();
+        List<Integer> path = new ArrayList<>();
+
+        int cur = start;
+        while (true) {
+            if (visited[cur]) {
+                break;
+            }
+
+            visited[cur] = true;
+            map.put(cur, path.size());
+            path.add(cur);
+            int next = arr[cur];
+            //다음 학생이 범위를 벗어나면 즉시 종료(ㅣ사이클 없으니까)
+            if (next < 1 || next > n) break;
+
+            if (!map.containsKey(next)) {
+                cur = next;
+                continue;
+            } else {
+                //사이클 발견
+                int idx = map.get(next);
+                answer += path.size() - idx;
+                break;
+            }
+        }
+    }
+}
+
+```