From da64bcb5cf504918fcd75e23bdd7042b1f2e09af Mon Sep 17 00:00:00 2001
From: mabhinav004 <59362898+mabhinav004@users.noreply.github.com>
Date: Sun, 10 Oct 2021 19:00:19 +0530
Subject: [PATCH] union_and_find_approach_graph

Detects cycle in O(n) amortized time complexity.
---
 Java/union_and_find_approach_graph | 57 ++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 Java/union_and_find_approach_graph

diff --git a/Java/union_and_find_approach_graph b/Java/union_and_find_approach_graph
new file mode 100644
index 0000000..1ad88b1
--- /dev/null
+++ b/Java/union_and_find_approach_graph
@@ -0,0 +1,57 @@
+
+//Detects cycle in O(n) amortized time complexity.
+
+import java.util.*;
+import java.lang.*;
+import java.io.*;
+
+class Solution
+{
+    //Function to detect cycle in an undirected graph.
+    public boolean isCycle(int V, ArrayList<ArrayList<Integer>> adj)
+    {       
+    
+        //Union find
+        
+        int[] parent=new int[V];
+        
+        Arrays.fill(parent,-1);   
+        
+        for(int src=0;src<V;src++){
+            
+            for(int des:adj.get(src)){
+                
+                if(src<des){
+                    
+                    int x=find(parent,src);
+                    int y=find(parent,des);
+                    
+                    if(x==y) return true;
+                    
+                    union(parent,x,y);
+                    
+                }
+                
+            }
+            
+        }
+        return false;
+    }
+    
+    private int find(int[] parent,int i){
+        
+        if(parent[i]==-1){
+            return i;
+        }
+        int idx=find(parent,parent[i]);
+        parent[i]=idx;
+        return idx;
+    }
+    
+    private void union(int[] parent,int x,int y){
+        
+        parent[x]=y;
+        
+    }
+    
+}