이예진: [BOJ] 9466 텀 프로젝트_241121

Author: yeahdy

BOJ/5001-10000번/YJ_9466.java

@@ -0,0 +1,62 @@
+import java.io.*;
+import java.util.*;
+
+//2 ≤ n ≤ 10^5
+public class YJ_9466 {
+    static int[] graph;
+    static boolean[] visited;
+    static boolean[] isFinished;
+    static boolean[] isGrouping;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        int T = Integer.parseInt(st.nextToken());
+
+        //테스트케이스 실행
+        while(T-- > 0){
+            //초기화
+            int n = Integer.parseInt(br.readLine());
+            graph = new int[n+1];
+            isFinished = new boolean[n+1];
+            visited = new boolean[n+1];
+            isGrouping = new boolean[n+1];
+            st = new StringTokenizer(br.readLine());
+            for(int i=1; i<n+1; i++){
+                graph[i] = Integer.parseInt(st.nextToken());
+            }
+            //dfs 탐색
+            for(int i=1; i<n+1; i++){
+                if(!visited[i]){
+                    dfs(i);
+                }
+            }
+            //프로젝트 팀에 속하지 못한 학생 수
+            int count = 0;
+            for(int i=1; i<n+1; i++){
+                if(!isGrouping[i]){
+                    count++;
+                }
+            }
+            System.out.println(count);
+        }
+
+    }
+
+    public static void dfs(int current){
+        visited[current] = true;
+        int next= graph[current];
+
+        if(!visited[next]){
+            dfs(next);
+        } else if(!isFinished[next]) {    //★재방문이지만 이전에 사이클을 이미 만들었거나, 사이클 형성을 못한 경우
+            //싸이클 형성 가능 또는 자기자신
+            while(!isGrouping[next]){
+                isGrouping[next] = true;
+                next = graph[next];
+            }
+        }
+        isFinished[current] = true;
+    }
+
+}