<3> : 프로그래머스 도넛과 그래프

mjj111/DonutWithGraph.java

@@ -0,0 +1,78 @@
+// 3시 13분 시작 3시 54분 완료  약 40분 소요
+// 정점 도넛 막대 8자 그래프 반환
+// 정점 개수 100만개
+import java.util.*;
+class DonutWithGraph {
+    public int[] solution(int[][] edges) {
+        Map<Integer, Node> nodes = new HashMap<>();
+
+        for(int[] edge : edges) {
+            int start = edge[0];
+            int end = edge[1];
+
+            Node startNode;
+            if(!nodes.containsKey(start)) {
+                nodes.put(start, new Node(0,0));
+            }
+            startNode = nodes.get(start);
+
+            Node endNode;
+            if(!nodes.containsKey(end)) {
+                nodes.put(end, new Node(0,0));
+            }
+            endNode = nodes.get(end);
+
+            endNode.indegree++;
+            startNode.next++;
+            startNode.nexts.add(end);
+        }
+
+        int middleNodeIndex = 0;
+        int total = 0;
+        int eight = 0;
+        int line = 0;
+        int donut = 0;
+        int wannaRemove = 0;
+        for(Integer nodeIndex : nodes.keySet()) {
+            Node now = nodes.get(nodeIndex);
+            if(now.indegree == 0 && now.next >= 2) {
+                middleNodeIndex = nodeIndex;
+                total = now.next;
+
+                wannaRemove = nodeIndex;
+
+                for(int next : now.nexts) {
+                    nodes.get(next).indegree--;
+                }
+            }
+        }
+        nodes.remove(wannaRemove);
+
+        for(int nodeIndex : nodes.keySet()) {
+            Node now = nodes.get(nodeIndex);
+            if(now.indegree == 0) {
+                line++;
+            }
+            if(now.indegree == 2 && now.next == 2) {
+                eight++;
+            }
+        }
+
+        donut = total - eight - line;
+        // 정점 도넛 막대 8자 그래프 반환
+        int[] answer = new int[]{middleNodeIndex,donut, line, eight};
+        return answer;
+    }
+
+    class Node {
+        int indegree;
+        int next;
+        ArrayList<Integer> nexts = new ArrayList<>();
+
+        Node(int indegree, int next) {
+            this.indegree = indegree;
+            this.next = next;
+        }
+    }
+}
+