Merge pull request #141 from AlgorithmWithGod/suyeun84

[20250218] BOJ / G4 / 키 순서 / 김수연

Author: ShinHeeEul

suyeun84/202502/18 BOJ G4 키 순서.md

@@ -0,0 +1,62 @@
+```java
+import java.util.*;
+import java.io.*;
+
+public class Main {
+
+	public static void main(String[] args) throws Exception {
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		StringTokenizer st = new StringTokenizer(br.readLine());
+		
+		int N = Integer.parseInt(st.nextToken());
+		int M = Integer.parseInt(st.nextToken());
+		int answer = 0;
+		ArrayList<ArrayList<Integer>> maxgraph = new ArrayList<>(N+1);
+		ArrayList<ArrayList<Integer>> mingraph = new ArrayList<>(N+1);
+		for (int i = 0; i < N+1; i++) {
+			maxgraph.add(new ArrayList<>());
+			mingraph.add(new ArrayList<>());
+		}
+		for (int i = 0 ; i < M; i++) {
+			st = new StringTokenizer(br.readLine());
+			int a = Integer.parseInt(st.nextToken());
+			int b = Integer.parseInt(st.nextToken());
+			mingraph.get(b).add(a);
+			maxgraph.get(a).add(b);
+		}
+		for (int i = 1; i <= N; i++) {
+			Queue<Integer> q = new LinkedList<>();
+			q.add(i);
+			boolean[] visited = new boolean[N+1];
+			int mincnt = 0;
+      visited[i] = true;
+			while (!q.isEmpty()) {
+				int curr = q.poll();
+				for (int k : mingraph.get(curr)) {
+					if (!visited[k]) {
+						q.add(k);
+						visited[k] = true;
+						mincnt++;
+					}
+				}
+			}
+			int maxcnt = 0;
+			q.add(i);
+			Arrays.fill(visited, false);
+      visited[i] = true;
+			while (!q.isEmpty()) {
+				int curr = q.poll();
+				for (int k : maxgraph.get(curr)) {
+					if (!visited[k]) {
+						q.add(k);
+						visited[k] = true;
+						maxcnt++;
+					}
+				}
+			}
+			if (mincnt + maxcnt == N-1) answer++;
+		}
+		System.out.println(answer);
+	}
+}
+```