From 77f138077be3004fa6c0df5aa530dbc95384826f Mon Sep 17 00:00:00 2001
From: Shubhojeet Banerjee <50337427+Shubhojeetban@users.noreply.github.com>
Date: Sat, 23 Oct 2021 15:04:56 +0530
Subject: [PATCH] Add Check Bipartite in Graph (#2708)

---
 DataStructures/Graphs/BipartiteGrapfDFS.java | 80 ++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 DataStructures/Graphs/BipartiteGrapfDFS.java

diff --git a/DataStructures/Graphs/BipartiteGrapfDFS.java b/DataStructures/Graphs/BipartiteGrapfDFS.java
new file mode 100644
index 00000000..472f20f1
--- /dev/null
+++ b/DataStructures/Graphs/BipartiteGrapfDFS.java
@@ -0,0 +1,80 @@
+package DataStructures.Graphs;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.Arrays;
+
+/**
+ * Given an adjacency list of a graph adj  of V no. 
+ * of vertices having 0 based index. 
+ * Check whether the graph is bipartite or not.
+ * 
+ * Input : 
+ * {{0, 1, 0, 1},
+ *  {1, 0, 1, 0},
+ *  {0, 1, 0, 1},
+ *  {1, 0, 1, 0}}
+ * 
+ * Output : YES
+ */
+public class BipartiteGrapfDFS {
+    private static boolean bipartite(int V, ArrayList<ArrayList<Integer>>adj, int[] color, int node){
+        if(color[node] == -1){
+            color[node] = 1;
+        }
+        for(Integer it : adj.get(node)){
+            if(color[it] == -1){
+                color[it] = 1-color[node];
+                if(bipartite(V, adj, color, it)== false) return false;
+            }
+            else if(color[it] == color[node]){
+                return false;
+            }
+        }
+        return true;
+    }
+    public static boolean isBipartite(int V, ArrayList<ArrayList<Integer>> adj)
+    {
+        // Code here
+        int[] color = new int[V+1];
+        Arrays.fill(color, -1);
+        
+        for(int i =0; i< V; i++){
+            if(color[i] == -1){
+                if(!bipartite(V, adj, color, i)){
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+    public static void main(String[] args) throws IOException {
+        BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
+        int t = Integer.parseInt(read.readLine().trim());
+        while(t-- > 0) {
+            String[] S = read.readLine().trim().split(" ");
+            int V = Integer.parseInt(S[0]);
+            int E = Integer.parseInt(S[1]);
+            
+            ArrayList<ArrayList<Integer>> adj = new ArrayList<>();
+            for(int i =0;i < V; i++) {
+                adj.add(new ArrayList<>());
+            }
+            for(int i = 0; i < E; i++) {
+                String[] s = read.readLine().trim().split(" ");
+                int u = Integer.parseInt(s[0]);
+                int v = Integer.parseInt(s[1]);
+                adj.get(u).add(v);
+                adj.get(v).add(u);
+            }
+            
+            boolean ans = isBipartite(V, adj);
+            if(ans)
+                System.out.println("YES");
+            else
+                System.out.println("NO");
+        }
+    }
+}