### Coding Interview Questions Set 3

For previous  questions and answers please refer to  Coding Interview Questions Set 1 and
Coding Interview Set 2.
Let's begin with set 3,

7)How to reverse a singly linked list?

a)Simple recursive solution:

}
}

b)Iterative solution:

var prev = null;
}
return prev;
}

8)Given a column title, return its corresponding column number. (Asked in Microsoft)
Write a function that accepts a string s.
Constraints:
1 <= s.length <= 7
s consists only of uppercase English letters.
s is between "A" and "FXSHRXW".

For example:

A -> 1
B -> 2
C -> 3
...
Z -> 26
AA -> 27
AB -> 28

Example 1:

Input: "A"
Output: 1

Example 2:
Input: "AB"
Output: 28

Example 3:
Input: "ZY"
Output: 701

Solution:
var titleToNumber = function(s) {
const charCodeBase = 'A'.charCodeAt(0);
const n = s.length;
let result = 0;
for (let i = 0; i < n; i++){
result = result * 26 + (s.charCodeAt(i) - charCodeBase + 1);
}
return result ;
};
The charCodeAt() method returns the Unicode of the character
at the specified index in a string.
Logic:
Think of it as base 26.
For example,
Column number of "AB" = 1 * 26^1 + 2 * 26^0

Please stay connected for coding interview questions set 4.

Written By:

Saurabh Joshi

### Node JS:Understanding bin in package.json.

Well as a Node Js developer we know package.json as dependency file where we keep a note of all dependencies of our project. Here we will be looking at what is bin in package.json? To understand this we first need to understand command line application and it's purpose. CLI applications are mostly used to automate things such as deployments of application,running tests,building reports and the list goes on and on. So lets start with creating our first CLI application. First, let’s make sure you have the tools required. To complete this tutorial, you will need the following: 1)A recent version of Node.js downloaded and installed 2)A good text editor, such as Visual Studio Code Next, open your computer’s command prompt (Windows) or terminal (macOS/Linux). Change the current directory to the folder where you save your documents or projects. Enter the following commands to create a new project folder and initialize the project. mkdir hello-cli cd hello-cli npm init Nex

### Node.js: Extract text from image using Tesseract.

In this article, we will see how to extract text from images using Tesseract . So let's start with this use-case, Suppose you have 300 screenshot images in your mobile which has an email attribute that you need for some reason like growing your network or for email marketing. To get an email from all these images manually into CSV or excel will take a lot of time. So now we will check how to automate this thing. First, you need to install Tesseract OCR( An optical character recognition engine ) pre-built binary package for a particular OS. I have tested it for Windows 10. For Windows 10, you can install  it from here. For other OS you make check  this link. So once you install Tesseract from windows setup, you also need to set path variable probably, 'C:\Program Files\Tesseract-OCR' to access it from any location. Then you need to install textract library from npm. To read the path of these 300 images we can select all images and can rename it to som