# online classes

## Make anagrams from two Strings

Problem Statement Given two strings, find the total number of characters we need to delete from these strings to make them anagrams of each other. Understanding Anagrams Anagrams are defined with respect to a given string of characters (not necessarily characters in the English Alphabet) but a wider set of characters may be. Given two strings A and B, if the number of time each character occurs in both the string is exactly same, we say A and B are anagrams. However, the order in which the character appears may be different and doesn't matter. For example A = axbbxxcecdeedda B = abacb...
Read More

## Matrix Rotation and Matrix Transpose

Problem Definition – Matrix Rotation (by 90, 180, 270 degrees) This is a very famous interview question and has been asked numerous times. We are trying to solve the problem of matrix rotations where the inputs are as follows: A matrix of dimension M * N A number from the set (90, 180, ,270) by which we need to rotate the matrix. For simplicity we will consider a matrix to be a 2 dimensional array of integers. What does it mean to rotate a matrix? This can only be explained by nice diagrams. Just for a formal definition, I would say that matrix rotation is a structural re-arrangeme...
Read More

## Inorder Predecessor of node in Binary Tree Using Parent Pointer

Introduction This is the seventh article in the Tree Traversals - Online Classes. This article presents ways to find out inorder predecessor of node in binary tree. As we have already read about the Inorder Successor it wont take much effort to understand the predecessor. Definition - Inorder Predecessor of node in Binary Tree If a node K is called the inorder predecessor of node N then N must be visited immediately after K in a inorder traversal of the tree. Below is a more formal definition of Inorder Predecessor: If the node has a left sub-tree, then inorder predecessor is the ...
Read More

## Complex Graph Operations

Introduction This is the fourth article in the Graph Theory - Online Classes. After learning the basic graph operations, its time to dive deeper and have some understanding about the complex operations which we can be done over a graph or a set of graphs. To learn about the basics you can always visit Graph Theory Basics. Complex Graph Operations Union of Graphs The union of two graphs G(VG, EG) and H(VH, EH) is the union of their vertex sets and their edge families. Which means G ∪ H = (VG ∪ VH, EG ∪ EH). The below image shows a union of graph G and graph H. Make sure that all the v...
Read More

## Graph Operations

Introduction This is the third article in the Graph Theory - Online Classes. With some basic concepts we learnt in the previous two articles listed here in Graph Theory, now we have enough tools to discuss some operations on any graph. In this article we will try to define some basic operations on the Graph. Graph Operations - Extracting sub graphs In this section we will discuss about various types of sub graphs we can extract from a given Graph. Sub graph Getting a sub graph out of a graph is an interesting operation. A sub graph of a graph G(V,E) can be obtained by the following...
Read More