[Graph] baekjoon-21276

Author: Seogeurim

README.md

@@ -4,6 +4,11 @@
 ![GitHub commit activity](https://img.shields.io/github/commit-activity/m/Seogeurim/Algorithm-practice)
 ![GitHub top language](https://img.shields.io/github/languages/top/Seogeurim/Algorithm-practice?color=yellow&logo=Java)
 
+> Commit 수 ≅ 푼 문제의 수
+>
+> 🏅  **300 Commits !!** 2021-03-31  
+> 🏃‍♀️  _Running for 400 commits..._
+
 ### 📖 [NOTES 바로가기](./notes)
 
 🔍 각 문제를 클릭하면 풀이 및 코드를 볼 수 있습니다.  
@@ -257,6 +262,7 @@
 | 05  |     | [Programmers 네트워크](./src/Graph/prg43162)             | union-find       |
 | 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) |
 
 ### Minimum Spanning Tree (MST)
 

src/Graph/P21276/Main.java

@@ -0,0 +1,76 @@
+package Graph.P21276;
+
+import java.io.BufferedReader;
+import java.io.FileInputStream;
+import java.io.InputStreamReader;
+import java.util.*;
+
+public class Main {
+
+    static int N, M;
+    static String[] names;
+    static HashMap<String, Integer> idx = new HashMap<>();
+
+    static LinkedList<Integer>[] children, graph;
+    static int[] indegree;
+
+    public static void main(String[] args) throws Exception {
+        System.setIn(new FileInputStream("src/Graph/P21276/input.txt"));
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+
+        N = Integer.parseInt(br.readLine());
+        names = new String[N];
+        children = new LinkedList[N];
+        graph = new LinkedList[N];
+        indegree = new int[N];
+
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        for (int i = 0; i < N; i++) names[i] = st.nextToken();
+
+        Arrays.sort(names);
+        for (int i = 0; i < N; i++) {
+            idx.put(names[i], i);
+            children[i] = new LinkedList<>();
+            graph[i] = new LinkedList<>();
+        }
+
+        M = Integer.parseInt(br.readLine());
+        while (M-- > 0) {
+            st = new StringTokenizer(br.readLine());
+            int X = idx.get(st.nextToken()), Y = idx.get(st.nextToken());
+            graph[Y].add(X);
+            indegree[X] ++;
+        }
+
+        Queue<Integer> q = new LinkedList<>();
+        LinkedList<Integer> root = new LinkedList<>();
+        for (int i = 0; i < N; i++) {
+            if (indegree[i] == 0) {
+                q.offer(i);
+                root.add(i);
+            }
+        }
+
+        while (!q.isEmpty()) {
+            int cur = q.poll();
+            for (int next : graph[cur]) {
+                indegree[next] --;
+                if (indegree[next] == 0) {
+                    children[cur].add(next);
+                    q.offer(next);
+                }
+            }
+        }
+
+        System.out.println(root.size());
+        for (Integer s : root) System.out.print(names[s] + " ");
+        System.out.println();
+
+        for (int i = 0; i < N; i++) {
+            System.out.print(names[i] + " " + children[i].size() + " ");
+            Collections.sort(children[i]);
+            for (Integer c : children[i]) System.out.print(names[c] + " ");
+            System.out.println();
+        }
+    }
+}

src/Graph/P21276/README.md

@@ -0,0 +1,7 @@
+## [baekjoon-21276] 계보 복원가 호석
+
+![image](https://user-images.githubusercontent.com/22045163/113163622-4cad7180-927b-11eb-80c4-628a5a2d8b20.png)
+
+이 문제는 위상정렬 + Map 자료구조를 사용하는 문제이다. 위상정렬 문제라는 것을 떠올리기 힘들었다. 더 공부하도록 !!!
+
+![image](https://user-images.githubusercontent.com/22045163/113163695-5b942400-927b-11eb-9f80-e19a17d4fbee.png)

src/Graph/P21276/input.txt

@@ -0,0 +1,10 @@
+7
+daeil sangdo yuri hoseok minji doha haeun
+7
+hoseok sangdo
+yuri minji
+hoseok daeil
+daeil sangdo
+haeun doha
+doha minji
+haeun minji