[20251002] PGM / Lv2 / 도넛과 막대 그래프 / 이강현

[20251002] PGM / Lv2 / 도넛과 막대 그래프 / 이강현

Author: lkhyun

lkhyun/202510/02 PGM Lv2 도넛과 막대 그래프.md

@@ -0,0 +1,72 @@
+```java
+import java.util.*;
+class Solution {
+    static Map<Integer,List<Integer>> adjList = new HashMap<>();
+    static Map<Integer,Boolean> visited = new HashMap<>();
+    static Set<Integer> startCandidate = new TreeSet<>();
+    static Set<Integer> noStart = new TreeSet<>();
+    static int[] answer = new int[4];
+    
+    public int[] solution(int[][] edges) {
+        
+        for(int[] edge : edges){
+            List<Integer> temp;
+            if(adjList.containsKey(edge[0])){
+                startCandidate.add(edge[0]);
+                temp = adjList.get(edge[0]);
+            }else{
+                temp = new ArrayList<>();
+            }
+            temp.add(edge[1]);
+            adjList.put(edge[0],temp);
+            visited.put(edge[0],false);
+            visited.put(edge[1],false);
+        }
+        for(int[] edge : edges){
+            if(startCandidate.contains(edge[1])){
+                noStart.add(edge[1]);
+            }
+        }
+        for(int start : startCandidate){
+            if(!noStart.contains(start)){
+                answer[0] = start;
+                break;
+            }
+        }
+        
+        for(int start : adjList.get(answer[0])){
+            BFS(start);
+        }
+        return answer;
+    }
+    public void BFS(int start){
+        ArrayDeque<Integer> q = new ArrayDeque<>();
+        q.offer(start);
+        visited.put(start,true);
+        
+        while(!q.isEmpty()){
+            int cur = q.poll();
+            if(adjList.get(cur) == null){
+                answer[2]++;
+                return;
+            }
+            for(int next : adjList.get(cur)){
+                if(adjList.get(next) == null){
+                    answer[2]++;
+                    return;
+                }
+                if(adjList.get(next).size() == 2){
+                    answer[3]++;
+                    return;
+                }
+                if(visited.get(next)){
+                    answer[1]++;
+                    return;
+                }
+                q.offer(next);
+                visited.put(next,true);
+            }
+        }
+    }
+}
+```