diff --git a/dp/knapsack.java b/dp/knapsack.java
new file mode 100644
index 0000000..ddd9772
--- /dev/null
+++ b/dp/knapsack.java
@@ -0,0 +1,65 @@
+package dp;
+
+public class knapsack {
+
+	public static void main(String[] args) {
+		
+		int W = 10;
+		int w[] = {1, 3, 4, 6};
+		int v[] = {20, 30, 10, 50};
+		
+		System.out.println(maxProfit1(W, w, v, w.length));
+	}
+	
+	
+//	Using Recursion 
+//	Time complexity = 2^n	
+	static int maxProfit(int W, int w[], int v[], int n) {
+//		W is Bag Capacity, Array w and v contains weight and value of item respectively
+//		and n is number of items 
+		
+		if(W == 0 || n == 0) {
+			return 0 ;
+		}
+		
+		if(w[n-1] > W) {
+			return maxProfit(W, w, v, n-1);
+		}
+		else {
+			return Math.max((v[n-1] + maxProfit(W-w[n-1], w, v, n-1)), 
+							maxProfit(W, w, v, n-1));
+		}
+	}
+
+	
+//	Using DP
+//	Time complexity = n * W
+	static int maxProfit1(int W, int w[], int v[], int n) {
+		int dp[][] = new int [n+1][W+1] ;
+		
+		for(int i=0 ; i<=n ; i++) {
+			for(int j=0 ; j<=W ; j++) {
+				if(i == 0 || j == 0) {
+					dp[i][j] = 0 ;
+				} 
+				else if(w[i-1] <= j) {
+					dp[i][j] = Math.max(v[i-1] + dp[i - 1][j - w[i - 1]],
+							   dp[i - 1][j]) ;
+				} else {
+					dp[i][j] = dp[i-1][j] ;
+				}
+				
+			}
+		}
+//		To check what is in dp array
+		
+//		for(int i=0 ; i<=n ; i++) {
+//			for(int j=0 ; j<=W ; j++) {
+//				System.out.print(dp[i][j] + " ");
+//			}
+//			System.out.println();
+//		}
+		
+		return dp[n][W] ;
+	}
+}
diff --git a/maths/CatalanNumbers.java b/maths/CatalanNumbers.java
new file mode 100644
index 0000000..cb72928
--- /dev/null
+++ b/maths/CatalanNumbers.java
@@ -0,0 +1,60 @@
+package mathematics;
+
+public class CatalanNumbers {
+	
+//	Catalan numbers = Sequence of natural no's that occurs in many 
+//	interesting counting problems
+	
+//	eg : 1, 1, 2, 5, 14, 42, 132, 429, 1430....
+//	C(0) = 1
+//	C(n+1) = Σ C(i)*C(n-i) i=0 to n
+
+//	C(4) = C(0)C(3) + C(1)C(2) + C(2)C(1) + C(3)C(0)
+//		 = 14
+	
+	public static void main(String[] args) {
+		
+		System.out.println(catalanNumber(8));
+		System.out.println(catalanNumbers(7));
+
+	}
+	
+//	Method-1 Using Recursion 
+//	Time complexity = Σ T(i)*T(n-i-1) i=0 to n-1
+	
+	static int catalanNumber(int n) {
+		int res = 0 ;
+		
+		if(n <= 1) {
+			return 1 ;
+		}
+		
+		for(int i=0 ; i<n ; i++) {
+			res += catalanNumber(i)*catalanNumber(n-i-1) ;
+		}
+		
+		return res ;
+	}
+
+//	Method-2 Using Binomial Coefficient 
+//	Time complexity = O(n)
+	
+	static int binomialCoefficient (int n , int r) {
+		int res = 1 ;
+		
+		if(r > n-r ){
+			r = n - r ; 
+		}
+		
+		for(int i=0 ; i<r ; i++) {
+			res *= n-i ;
+			res /= i+1 ;
+		}
+		
+		return res ;
+	}
+	
+	static int catalanNumbers(int n) {
+		return binomialCoefficient(2*n,n) / (n+1) ;
+	}
+}
diff --git a/trees/VerticalSum.java b/trees/VerticalSum.java
new file mode 100644
index 0000000..5476812
--- /dev/null
+++ b/trees/VerticalSum.java
@@ -0,0 +1,58 @@
+import java.util.* ;
+
+public class VerticalSum {
+	
+	static Scanner sc = null ;
+
+	public static void main(String[] args) {
+		
+		sc = new Scanner (System.in);
+		
+		Node root = new Node(1);
+		root.left = new Node(2);
+		root.right = new Node(3);
+		root.right.left = new Node(5);
+		root.right.right = new Node(6);
+		root.right.left.left = new Node(7);
+		root.right.left.right = new Node(8);
+		
+		System.out.println(verticalSum(root)) ;
+
+	}
+	
+	
+    public static ArrayList <Integer> verticalSum(Node root) {
+        
+        ArrayList <Integer> ans = new ArrayList<>() ;
+        
+        if(root == null) return ans;
+        
+        TreeMap <Integer , Integer> a = new TreeMap <>();
+        verticalh(root , 0 , a);
+        
+        ans = new ArrayList<>(a.values()) ;
+        return ans ;
+    }
+    
+    public static void verticalh(Node root , int h , TreeMap<Integer , Integer> a) {
+        if(root == null) return ;
+        
+        verticalh(root.left , h-1 , a) ;
+        
+        int prevSum = ( a.get(h) == null ) ? 0 : a.get(h) ;
+        
+        a.put(h , prevSum + root.data);
+        
+        verticalh(root.right , h+1 , a) ;
+    }
+
+}
+
+class Node {
+	Node left , right ;
+	int data ;
+	
+	public Node(int data) {
+		this.data = data ;
+	}
+}