[Graph] baekjoon-2458

Author: Seogeurim

Diff for: README.md

@@ -276,6 +276,7 @@
 | 06  |     | [SWEA-3289 서로소 집합](./src/Graph/swea3289)            | union-find        |
 | 07  |     | [JUNGOL-1863 종교](./src/Graph/jo1863)                  | union-find : union-by-rank |
 | 08  |     | [Baekjoon-21276 계보 복원가 호석](./src/Graph/P21276)      | [위상정렬](./notes/Graph/TopologicalSort.md) |
+| 09  | ⭐️  | [Baekjoon-2458 키 순서](./src/Graph/P2458)               |                  |
 
 ### Minimum Spanning Tree (MST)
 

Diff for: src/Graph/P2458/Main.java

@@ -0,0 +1,57 @@
+package Graph.P2458;
+
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    static int N, M, next_cnt;
+    static LinkedList<Integer>[] graph;
+    static int[] cnt;
+    static boolean[] visited;
+
+    public static void main(String[] args) throws Exception {
+        System.setIn(new FileInputStream("src/Graph/P5643/input.txt"));
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+
+        graph = new LinkedList[N+1];
+        cnt = new int[N+1];
+        for (int i = 1; i <= N; i++) {
+            graph[i] = new LinkedList<>();
+        }
+
+        while (M-- > 0) {
+            st = new StringTokenizer(br.readLine());
+            graph[Integer.parseInt(st.nextToken())].add(Integer.parseInt(st.nextToken()));
+        }
+
+        for (int i = 1; i <= N; i++) {
+            visited= new boolean[N+1];
+            next_cnt = 0;
+            dfs(i);
+            cnt[i] += next_cnt;
+        }
+
+        int ans = 0;
+        for (int i = 1; i <= N; i++) {
+            if (cnt[i] == N) ans ++;
+        }
+
+        System.out.println(ans);
+    }
+
+    static void dfs(int cur) {
+        visited[cur] = true;
+        next_cnt ++;
+        for (int next : graph[cur]) {
+            if (!visited[next]) {
+                cnt[next] ++;
+                dfs(next);
+            }
+        }
+    }
+}

Diff for: src/Graph/P2458/README.md

@@ -0,0 +1,5 @@
+## [baekjoon-2458] 키 순서
+
+![image](https://user-images.githubusercontent.com/22045163/115832330-bcafb180-a44d-11eb-9cdc-3b736178cbd4.png)
+
+![image](https://user-images.githubusercontent.com/22045163/115832369-ca653700-a44d-11eb-8322-a91daa866817.png)

Diff for: src/Graph/P2458/input.txt

@@ -0,0 +1,7 @@
+6 6
+1 5
+3 4
+5 4
+4 2
+4 6
+5 2