chore(Java): add Catalan Numbers and Priority queue (#577)

algorithms/Java/Maths/catalan-numbers.java

@@ -0,0 +1,39 @@
+// Program to print Catalan Numbers till n using recursive approach.
+
+import java.util.*;
+
+class CatalanNumbers{
+
+	public static int findCat(int n){
+
+		int val = 0;
+
+		if (n<=1) return 1;
+
+		for (int i=0;i<n;i++){
+
+			val+= findCat(i)*findCat(n-i-1);
+		}
+
+		return val;
+	}
+
+
+	public static void main(String[] args) {
+		Scanner sc = new Scanner(System.in);
+		int n = sc.nextInt();
+
+		for (int i=0;i<=n;i++) System.out.print(findCat(i)+" "); 
+
+	}
+
+
+
+}
+
+/* Applications of Catalan Numbers
+	-Number of possible full binary trees with n+1 leaves
+	-Number of possible Binary Search Trees with n nodes
+	-Number of ways a convex polygon of n+2 sides can be split into triangles by connecting vertices
+	-Refer this link for more :- https://iq.opengenus.org/applications-of-catalan-numbers/
+*/	

algorithms/Java/README.md

@@ -23,6 +23,7 @@
 
 ## Maths
 - [Factorial](Maths/factorial_using_big_integer.java)
+- [Catalan Numbers](Maths/catalan-numbers.java)
 
 ## Queues
 - [Circular Queue using Linked List](queues/circular-queue-linked-list.java)
@@ -31,7 +32,7 @@
 
 ## Scheduling
 - [Multi-Level Queue Scheduling](scheduling/multi-level-queue-scheduling.java)
-- [Rund Robin](scheduling/round-robin.java)
+- [Round Robin](scheduling/round-robin.java)
 
 ## Searching
 - [Binary Search](searching/binary-search.java)