Disjoin set algorithm added to graph section

Author: karthik124a

src/main/java/com/thealgorithms/graph/DisjointSet.java

@@ -0,0 +1,42 @@
+package com.thealgorithms.graph;
+
+public class DisjointSet {
+    int[] parent;
+    int[] rank;
+    public DisjointSet(int n){
+        parent = new int[n];
+        rank = new int[n];
+        for(int i=0; i<n; i++){
+            parent[i] = i;
+            rank[i] = 1;
+        }
+    }
+
+    int findLeader(int x){
+        if(parent[x]==x){
+            return parent[x];
+        }
+        int leader = findLeader(parent[x]);
+        parent[x] = leader;
+        return leader;
+    }
+
+    boolean isSame(int x, int y){
+        return findLeader(x)==findLeader(y);
+    }
+
+    void merge(int x, int y){
+        int xLeader = findLeader(x);
+        int yLeader = findLeader(y);
+        if(xLeader != yLeader){
+            if(rank[xLeader]<rank[yLeader]){
+                parent[xLeader] = yLeader;
+            }else{
+                parent[yLeader] = xLeader;
+                if(rank[xLeader] == rank[yLeader]){
+                    rank[xLeader] += 1;
+                }
+            }
+        }
+    }
+}