DEV Community: Anirudh Sharma

Add Binary (LeetCode #67)

Anirudh Sharma — Mon, 30 Nov 2020 14:28:45 +0000

Problem Statement

Given two binary strings a and b, return their sum as a binary string.

Approach

This is a straight forward problem. We will use the same approach that we use for adding two decimal numbers.

Below are the steps -

Keep a variable carry.
Scan the strings from right to left.
Calculate sum by adding the two bits represented by the characters and add carry to it.
Take the sum modulo 2 (sum % 2) (because it's binary, duh 😃) and add it in the front of the existing result string.
Update the carry by taking sum / 2 for the next iteration.
Check if the value of the carry is more than zero after the last iteration and if exists, add it to the front of the result.

And that's it! We have just added two binary srings. We should be proud of ourselves 👏.

The code in Java, JavaScript and Python is below -

Java

public class AddBinary {
    public String addBinary(String a, String b) {
        // Resultant String
        StringBuilder result = new StringBuilder();
        // Indices for a and b
        int i = a.length() - 1;
        int j = b.length() - 1;
        // Carry
        int carry = 0;
        while (i >= 0 || j >= 0) {
            // Sum of two bits
            int sum = carry;
            if (i >= 0) {
                sum += a.charAt(i--) - '0';
            }
            if (j >= 0) {
                sum += b.charAt(j--) - '0';
            }
            // Add the bit to the result
            result.insert(0, sum % 2);
            // Modify carry
            carry = sum / 2;
        }
        // Final check if carry exists
        if (carry > 0) {
            result.insert(0, 1);
        }
        return result.toString();
    }
}

JavaScript

var addBinary = function (a, b) {
    // Resultant string
    let result = "";
    // Indices for a and b
    let i = a.length - 1;
    let j = b.length - 1;
    // Carry
    let carry = 0;
    while (i >= 0 || j >= 0) {
        // Sum of two bits
        let sum = carry;
        if (i >= 0) {
            sum += a[i--] - '0';
        }
        if (j >= 0) {
            sum += b[j--] - '0';
        }
        // Add the bit to the result
        result = sum % 2 + result;
        // Modify carry
        carry = parseInt(sum / 2);
    }
    // Final check if carry exists
    if (carry > 0) {
        result = 1 + result;
    }
    return result;
};

Python

class AddBinary:
    def addBinary(self, a: str, b: str) -> str:
        # Resultant string
        result = ""
        # Indices for a and b
        aCount = len(a) - 1
        bCount = len(b) - 1
        # Carry
        carry = 0
        # Loop for all the characters in the strings
        while aCount >= 0 or bCount >= 0:
            # Sum of two bits
            totalSum = carry
            if aCount >= 0:
                totalSum += int(a[aCount])
                aCount -= 1
            if bCount >= 0:
                totalSum += int(b[bCount])
                bCount -= 1
            # Add the bit to te result
            result = str(totalSum % 2) + result
            # Modify carry
            carry = totalSum // 2
        # Final check if carry exists
        if carry > 0:
            result = str(1) + result
        return result

Conclusion

I hope you enjoyed this post. Feel free to share your thoughts on this.

You can find the complete source code on my GitHub repository. If you like what you learn, feel free to fork 🔪 and star ⭐ it.

Feel free to connect with me on Twitter and LinkedIn.

Till next time… Happy coding 😄 and Namaste 🙏!

LeetCode Problems 11-20

Anirudh Sharma — Sun, 15 Nov 2020 12:13:33 +0000

Howdy happy people 👋! In the previous post, we looked at the first ten problems from LeetCode.

In this post, we will continue to make ourselves better by looking at the next ten problems.

[11] Container With Most Water
[12] Integer To Roman
[13] Roman To Integer
[14] Longest Common Prefix
[15] 3 Sum
[16] 3 Sum Closest
[17] Letter Combinations Of A Phone Number
[18] 4 Sum
[19] Remove Nth Node From End Of List
[20] Valid Parentheses

I hope you will find them useful. I have implemented the solutions to these problems in four programming languages - Java, Python, JavaScript and Kotlin.

You can find the complete source code on my GitHub repository. If you like what you learn, feel free to fork 🔪 and star ⭐ it.

Keep practicing... keep coding... stay safe and Namaste 🙏.

Follow me on Twitter to be in touch.

LeetCode Problems 1-10

Anirudh Sharma — Sun, 08 Nov 2020 07:05:37 +0000

Howdy fellow devs 👋! In order to improve every day, we must practice continuously of what we have learnt.
Solving problems on online learning platforms is one of the most common ways to do so.

LeetCode is one of the most widely used platforms for solving problems. They have a wide variety of problems of varying difficulty levels i.e., Easy, Medium and Hard.

I also try to solve each problem every day to keep my brain juices flowing 😃. Since humans tend to forget most of the information, it's only logical if we document the analysis of a problem, approach we took to solve that problem etc. Therefore, as soon as I solve the problem, I try to write a blog with all the information I used to solve that problem.

Below are the blog posts for LeetCode problems 1 - 10.

I hope you will find them useful. I have implemented the solutions to these problems in four programming languages - Java, Python, JavaScript and Kotlin.

You can find the complete source code on my GitHub repository. If you like what you learn, feel free to fork 🔪 and star ⭐ it.

Keep practicing... keep coding... stay safe and Namaste 🙏.

Read/Write Files In NodeJS

Anirudh Sharma — Tue, 27 Oct 2020 12:09:10 +0000

Hello fellow devs 👋! I am sure like me you find yourself in a position where you need to read from a file or write to a file in your day to day work.

In this post, we will understand and see the code snippets for these two tasks.

But how will we do that, you ask 🤔? Luckily for us, we have a File System (fs) module which is a part of the code library of Node JS.

One important thing, since it is a core module, we don’t have to install it explicitly. Cool, eh 😄?

Read From File

Reading from files is one of the most common things we do when we build an application using Node JS.

We can read files in two ways - asynchronous (non-blocking) and synchronous (blocking). Usually, the preferable way is non-blocking i.e., ask node to read a file, and then to get a callback when reading is finished.

Let's look at the code

// Import the module
const fs = require('fs');

// This function reads the file and prints the data on the
// console using the callback function
const readFile = () => {
    fs.readFile('files/sample-text-file.txt', 'utf8',
        (err, data) => {
            if (err) {
                return console.log(err);
            }
            console.log(data);
        });
}

module.exports = {
    readFile
};

Here, we are passing the path of the file to be read and the type of encoding.

If we wish to read the file synchronously then we can use the function readFileSync instead of readFile.

Write To File

Like reading from a file, a common use case is to write into a file. We can leverage the core File System (fs) Node JS module.

Here also, like reading, we have two ways - asynchronous (non-blocking) and synchronous (blocking).

Let's see the code for writing to a file asynchronously.

// Import the core node js fs module
const fs = require('fs');
// The content to be written into the file
const content = 'This content will be written into the file';

const writeFile = () => {
    fs.writeFile('files/sample-file-to-write.txt', content,
        (err) => {
            if (err) {
                throw err;
            }
            console.log('File is saved!');
        });
}

module.exports = {
    writeFile
};

Conclusion

And that's it! We are done with reading and writing files in NodeJS. Easy peasy, right?

You can find the complete code on my GitHub. If you find it useful, consider giving it a star ⭐.

Also, you can read more such handy posts on my personal blog.

Happy Learning 😊 and Namaste 🙏.