[20251005] BOJ / G4 / 거짓말 / 김수연

Author: suyeun84

suyeun84/202510/05 BOJ G4 거짓말.md

@@ -0,0 +1,72 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    static StringTokenizer st;
+    static void nextLine() throws Exception { st = new StringTokenizer(br.readLine()); }
+    static int nextInt() { return Integer.parseInt(st.nextToken()); }
+
+    static int N, M;
+    static int[] parent;
+    static List<int[]> parties = new ArrayList<>();
+
+    public static void main(String[] args) throws Exception {
+        nextLine();
+        N = nextInt();
+        M = nextInt();
+
+        parent = new int[N + 1];
+        for (int i = 1; i <= N; i++) parent[i] = i;
+
+        nextLine();
+        int T = nextInt();
+        int[] truth = new int[T];
+        for (int i = 0; i < T; i++) truth[i] = nextInt();
+
+        for (int i = 0; i < M; i++) {
+            nextLine();
+            int cnt = nextInt();
+            int[] attendees = new int[cnt];
+            for (int j = 0; j < cnt; j++) attendees[j] = nextInt();
+            parties.add(attendees);
+
+            for (int j = 1; j < cnt; j++) {
+                union(attendees[0], attendees[j]);
+            }
+        }
+
+        boolean[] truthRoot = new boolean[N + 1];
+        for (int t : truth) {
+            truthRoot[find(t)] = true;
+        }
+
+        int answer = 0;
+        for (int[] party : parties) {
+            boolean canLie = true;
+            for (int p : party) {
+                if (truthRoot[find(p)]) {
+                    canLie = false;
+                    break;
+                }
+            }
+            if (canLie) answer++;
+        }
+
+        System.out.println(answer);
+    }
+
+    static int find(int x) {
+        if (x == parent[x]) return x;
+        return parent[x] = find(parent[x]);
+    }
+
+    static void union(int x, int y) {
+        x = find(x);
+        y = find(y);
+        if (x == y) return;
+        parent[y] = x;
+    }
+}
+```