### Top view of a binary tree

In this post, we will discuss a method to print the Top view of a binary tree. This is one the most common easy level interview questions. Also, you might get to see interview questions which can be solved with slight variations to this code.

Top View of a tree is defined as the nodes that would be visible to us if we viewed the tree from the top. To do this we have to maintain horizontal distance of all the nodes from the root node and print the first node for each horizontal distance. This problem can be solved easily with simple traversal and use of data structures. Have a look at the below image to get some idea. Top view of a binary tree

In the above image, the horizontal distance of the root is set to 0 and for all the node to the right we increase the horizontal distance by 1 and for all the node to the right, we decrease the horizontal distance by 1. Thus, the problem reduces to printing the first node with a horizontal distance that is not been traversed before.

Let's have a look at the code.

### Sample input and output to check the program

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Bottom View of a Binary Tree
Left View of a Binary Tree
Right View of a Binary Tree

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2. ### Infix to Prefix conversion using Stack

This post is about conversion of Infix expression to Prefix conversion. For this conversion we take help of stack data structure, we need to push and pop the operators in and out of the stack.

Infix expressions are the expressions that we normally use,eg. 5+6-7; a+b*c etc. Prefix expressions are the expressions in which the 2 operands are preceded by the operator eg. -+567 , +a*bc etc.

This method is very similar to the method that we used to convert Infix to Postfix but the only difference is that here we need to reverse the input string before conversion and then reverse the final output string before displaying it.

NOTE: This changes one thing that is instead of encountering the opening bracket we now first encounter the closing bracket and we make changes accordingly in our code.

So, to convert an infix expression to a prefix expression we follow the below steps
(we have 2 string, 1st is the input infix expression string 2nd is the output string which is empty initially)

We first revers…

Hashing is a technique used for storing , searching and removing elements in almost constant time. Hashing is done with help of a hash function that generates index for a given input, then this index can be used to search the elements, store an element, or remove that element from that index.

A hash function is a function that is used to map the data elements to their position in the data structure used. For example if we use an array to store the integer elements then the hash function will generate position for each element so that searching, storing and removing operation on the array can be done in constant time that is independent of the number of elements in the array. For better look at the example below.

now we face a problem if for 2 numbers same position is generated example consider elements 1 and 14

1 % 13 = 1

14 % 13 = 1

so when we get 1 we store it at the first position, but when we get 14 we see that the position 1 is already taken, this is a case of collision.

Inorder…