# October 2020

## #30DaysofCode

• DSA

I had started the #30DaysofCode📚 challenge while I was revising the basic concepts, data structures, and solving easy problems on LeetCode. I documented this so that it helps both me and others to recall what we have learned. How to use this list📑 First, look at the given questions, if… Read More »#30DaysofCode

## Direct & Indirect Recursion

• DSA

In programming, Recursion means a function calling itself. The best use of recursion is when we have a big/complex problem and is solved by breaking down the problem into smaller instances. In this post, we’ll see direct and indirect recursion. Types of Recursion Generally, there are two main types of… Read More »Direct & Indirect Recursion

## Even Odd Separation O(N) Single Iteration

• DSA

Given an array containing a mix of even and odd numbers, and we need to perform Even Odd Separation. In this post we’ll see how to separate even and odd numbers in a single iteration using two pointers. Example Solution Approach Method 1 To separate even-odd elements, we can take… Read More »Even Odd Separation O(N) Single Iteration

## Tree Traversals – Preorder, Inorder, Postorder

• DSA

Tree Traversal: visiting every node of a tree. Unlike other linear data structures, where we traverse through every element in order, it’s not the same with the tree. Trees being non-linear data structures, there will always be more than one way to traverse through a tree. There are three types… Read More »Tree Traversals – Preorder, Inorder, Postorder

## Program to Evaluate Postfix Expression – LeetCode

• DSA

Given, an arithmetic expression. We need to Evaluate Postfix Expression, also known as Reverse Polish Notation. Operators include /,*,+,- and we will always return a finite result, there won’t be any divide with zero operations. Example What is a Postfix Expression A Postfix Expression or a Reverse Polish Notation is… Read More »Program to Evaluate Postfix Expression – LeetCode

## Balanced Parenthesis Program

• DSA

We have an expression that contains brackets and alphanumeric characters, and we need to check whether the parenthesis are balanced or not. Balanced Parenthesis means an equal number of opening and closing brackets. Example Solution Approach – Using Stack Why Stack Data Structure? Here, our priority is to find if… Read More »Balanced Parenthesis Program