From 1fc96de64dd88c0a67e55cee89c86c0f001b51ad Mon Sep 17 00:00:00 2001
From: Taranpreet Singh <47025523+taran-1407@users.noreply.github.com>
Date: Fri, 2 Oct 2020 17:35:57 +0530
Subject: [PATCH] Created ArticulationPoint.java

Created ArticulationPoint.java, expects graph to be generated in accordance with GraphBuilder makeGraph method.
---
 ArticulationPoint/ArticulationPoint.java | 37 ++++++++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 ArticulationPoint/ArticulationPoint.java

diff --git a/ArticulationPoint/ArticulationPoint.java b/ArticulationPoint/ArticulationPoint.java
new file mode 100644
index 0000000..a28f680
--- /dev/null
+++ b/ArticulationPoint/ArticulationPoint.java
@@ -0,0 +1,37 @@
+class ArticulationPoints{
+	private static int time;
+	private static int[] disc, low;
+	private static boolean[] visited;
+
+	public static boolean[] articulationPoints(int[][] graph){
+		int NumberOfNodes = graph.length;
+
+		time = -1;
+		disc = new int[NumberOfNodes];
+		low = new int[NumberOfNodes];
+		visited = new boolean[NumberOfNodes];
+		java.util.Arrays.fill(low, 2*NumberOfNodes);
+
+		boolean[] isAP = new boolean[NumberOfNodes];
+		for(int i = 0; i< NumberOfNodes; i++)if(!visited[i] && graph[i] != null)apUtil(graph, isAP, i, -1);
+		return isAP;
+	}
+
+	private static void apUtil(int[][] g, boolean[] isAP, int u, int p){
+		visited[u] = true;
+		disc[u] = low[u] = ++time;
+
+		int childCount = 0;
+		for(int v:g[u]){
+			if(!visited[v]){
+				apUtil(g, isAP, v, u);
+
+				low[u] = Math.min(low[u], low[v]);
+				childCount++;
+
+				if(p != -1 && low[v] >= disc[u])isAP[u] = true;
+			}else if(v != p)low[u] = Math.min(low[u], disc[v]);
+		}
+		if(p == -1 && childCount > 1)isAP[u] = true;
+	}
+}