DEV Community: Md. Shafiqul Islam

Sorting an array

Md. Shafiqul Islam — Tue, 02 Sep 2025 05:28:13 +0000

Given an array of integers, nums sorting the array without using any build in fuction.
Input: [-1, 0, 1, 2, -1, -4]
Output: [-4, -1, -1, 0, 1, 2]

I will use two approach for sorting array. Bubble sort and quick sort.

Thought Process:

Minimal Approach

Here i will use bubble sort algorithm to sort this array.
Compare adjacent element of the array.
If they are wrong order then swap like arr[j] to arr[j+1].
Keep swapping untill array is sorted.

Optimal Approach

I will use quick sort algorithm to sort this array.
Use Devide and conquer technique.
Pick a pivot element
Partition the array:
If element smaller then pivot move left side.
If element larger then pivot move right side.

Brute-force Approach:

Minimal Approach

for i = 0 to n-1
   for j = 0 to n-2
      if arr[j] > arr[j+1]
         swap(arr[j], arr[j+1])

Optimal Approach

quicksort(arr):
   if length(arr) <= 1 return arr

   pivot = arr[last]
   left = elements < pivot
   right = elements >= pivot

   return quicksort(left) + pivot + quicksort(right)

Visualization: [5, 3, 8, 4, 2]

Pick pivot=2
[5,3,8,4] | 2 | []
          ↓
Sort left: []            Sort right: [5,3,8,4]
                         Pivot=4
                         [3] | 4 | [5,8]

Final result:
[2] + [3,4,5,8] → [2,3,4,5,8]

Time and Space Complexity

Time Complexity: For bubble sort: O(n²) and quick sort: O(n log n)
Space Complexity: For bubble sort: O(1) and quick sort: O(log n).

JavaScript Solution

const bubbleSort = function (nums) {
  let n = nums.length;
  for (let i = 0; i < n - 1; i++) {
    for (let j = 0; j < n - i - 1; j++) {
      if (nums[j] > nums[j + 1]) {
        let temp = nums[j];
        nums[j] = nums[j + 1];
        nums[j + 1] = temp;
      }
    }
  }
  return nums;
};

const quickSort = function (nums) {
  let n = nums.length;
  if (n <= 1) return nums;
  let pivot = nums[n - 1];
  let left = [];
  let right = [];
  for (let i = 0; i < n - 1; i++) {
    if (nums[i] < pivot) {
      left.push(nums[i]);
    } else {
      right.push(nums[i]);
    }
  }

  return [...quickSort(left), pivot, ...quickSort(right)];
};

Diﬀerence between let, var and const keyword in javascript.

Md. Shafiqul Islam — Tue, 15 Apr 2025 10:41:37 +0000

Why did you choose JavaScript?

Md. Shafiqul Islam — Sun, 06 Apr 2025 09:59:18 +0000

JavaScript is one of the most widely-used and dynamic programming languages in the world. I chose it for several reasons:

🔁 Interpreted Language
JavaScript doesn’t require a compiler; it runs directly in the browser or Node.js, which makes development faster and easier to test.

🌍 Cross-Platform
It runs on all major browsers and operating systems. With the help of frameworks like React Native and Electron, JavaScript can even be used for mobile and desktop apps.

⚙️ Event-Driven & Asynchronous Programming
JavaScript's event loop and support for asynchronous operations (via callbacks, promises, and async/await) make it ideal for responsive web apps.

🌐 Full-Stack Capabilities
It runs on both the client and server side, which allows for building full-stack applications using just one language.

🔧 Rich Ecosystem
The npm (Node Package Manager) registry has over 1 million packages, making it easy to find libraries and tools for virtually any task.

📦 Modular Architecture
JavaScript supports modular coding via ES6 modules, improving maintainability and scalability of applications.

🧠 Easy to Learn
JavaScript has a simple syntax that's close to English, making it beginner-friendly.
Tons of free resources, tutorials, and interactive platforms (like freeCodeCamp, MDN, etc.) make it super accessible for new learners.

Greatest Common Divisor of Strings in Javascript

Md. Shafiqul Islam — Mon, 18 Nov 2024 05:26:21 +0000

Today, I solved the second problem of the LeetCode 75 series. I'd like to share how I approached this problem.

Problem Statement:
You are given two strings, str1 and str2. Return the largest string x such that x divides both str1 and str2.

Examples:

Input: str1 = "ABCABC", str2 = "ABC"
Output: "ABC"

Input: str1 = "ABABAB", str2 = "ABAB"
Output: "AB"

Input: str1 = "LEET", str2 = "CODE"
Output: ""
**
My Approach**

I divided my solution into three parts:

Check if a common divisor string exists:
First, I check if a common divisor exists by concatenating str1 + str2 and str2 + str1.

If the two concatenated strings are not equal, it means there is no common divisor, and the function returns an empty string ("").

Find the GCD length:
Next, I find the GCD of the lengths of str1 and str2.

I use a recursive gcd() function. If b !== 0, the function calls itself recursively with two arguments:
gcd(a, b) = gcd(b, a % b)
Once b = 0, the function returns a, which is the GCD length.

Example Calculation:

Initial Call: gcd(6, 3)
Since b = 3 is not 0, it recursively calls gcd(3, 6 % 3) → gcd(3, 0)

Second Call: gcd(3, 0)
Now b = 0, so the function returns 3.

Extract the GCD substring:
Finally, I extract the substring from str1 using the gcdlength.

function gcdOfStrings(str1, str2) {
  // recursive function to calculate the GCD of two numbers
  function gcd(a, b) {
    console.log(a, b);
    return b === 0 ? a : gcd(b, a % b);
  }

  // Step 1: Check if str1 and str2 match or not
  if (str1 + str2 !== str2 + str1) {
    return ""; // No common pattern exists
  }

  // Step 2: Find the GCD of the lengths of str1 and str2
  const len1 = str1.length;
  const len2 = str2.length;
  const gcdLength = gcd(len1, len2);

  // Step 3: The largest divisor substring
  return str1.substring(0, gcdLength);
}

// Example usage:
console.log(gcdOfStrings("ABCABC", "ABC")); // Output: "ABC"
console.log(gcdOfStrings("ABABAB", "ABAB")); // Output: "AB"
console.log(gcdOfStrings("LEET", "CODE")); // Output: ""

If you have better solutions or ideas, feel free to share with me.

Merge Strings Alternately in javascript

Md. Shafiqul Islam — Wed, 13 Nov 2024 05:29:02 +0000

After a long time, I'm back to solving problems in the LeetCode 75 series. Today, I solved the first problem, which was easy but had some tricky corner cases. I'd like to share how I approached this problem.

You are given two strings word1 and word2. Merge the strings by adding letters in alternating order, starting with word1. If a string is longer than the other, append the additional letters onto the end of the merged string.

Example:
Input: word1 = "abc",
word2 = "pqr"
Output: "apbqcr"

I divided my solution into three parts:

Logic check (corner case handling)
Using a for loop
Appending the final string

Logic check: First, I checked which word had the smallest length. I then iterated the loop based on this smallest length. If one word was longer than the other, I appended the remaining characters from the longer word to the end of the string.

Using a loop: I used a loop to alternate and merge characters from each string.

Appending the final string: Finally, I combined the strings and returned the result.

var mergeAlternately = function (word1, word2) {
  let str = "";

  if (word2.length > word1.length) {
    for (let i = 0; i < word1.length; i++) {
      str = str + word1[i] + word2[i];
    }
    str = str + word2.substring(word1.length);
  } else if (word1.length > word2.length) {
    for (let i = 0; i < word2.length; i++) {
      str = str + word1[i] + word2[i];
    }
    str = str + word1.substring(word2.length);
  } else {
    for (let i = 0; i < word1.length; i++) {
      str = str + word1[i] + word2[i];
    }
  }
  return str;
};

console.log("result", mergeAlternately("abcd", "pq"));

result: apbqcd

If you have better solutions or ideas, feel free to share with me.

TypeScript vs JavaScript

Md. Shafiqul Islam — Tue, 27 Feb 2024 09:22:45 +0000

Hello there, I am currently working on a piece comparing TypeScript and JavaScript. JavaScript and TypeScript are two of the most popular programming languages in the modern world, each with its distinct characteristics. In this content, I will delve into the significant differences between them.

What is Technology? What are the types of technology? How to use technology in our life.

Md. Shafiqul Islam — Mon, 20 Mar 2023 04:35:03 +0000

The combined result of science and engineering is what we call technology.

Like our widely used mobile phone or cell phone it is also a technology. Again the ancient stone wheel is also a technology. Again the abacus and a technology invented to aid in the large number of calculations used by the Babylonians around 2,400 BC.

In simple words, Technology is the application of scientific knowledge for the practical purpose of human life.

Types of technology:
1. Information Technology: Information technology refers to the use of computers, software and other digital technologies to store, process and transmit information.
2. Medical Technology: It refers to the development of new devices, equipment and treatments for the diagnosis, treatment and prevention of diseases
3. Industrial Technology: It refers to the development and use of machines, tools and other tools to produce goods and provide services.
4. Nanotechnology: This refers to the development of new materials, devices and systems at the nanoscale (typically less than 100 nanometers) with applications in fields such as electronics, medicine and energy.

Uses technology in our life:
We are using technology in our daily life. Let's take a look at some of the uses of technology.

1. Communication: One of the most essential areas in today's world is communication. Communication media has improved so much with the help of technology that the whole world has turned into a “Small Village” today. Mobile phones, telephones, faxes, emails, Facebook, WhatsApp, etc. are all the blessings of technology that we use today.
2. Education: Computers and the internet have transformed education in many ways today. Technologies are helping our child learn lessons and other things easily. A wide range of educational applications are now being made available for educational purposes. Now lessons can be learned online with the help of videos and webinars.
3. Health: Technology is driving our medical science in a new direction. Medical science is improving by inventing new equipment. There are also various apps available for you to manage diabetes, high blood pressure and other issues. Not only that, they have made it possible for you to consult your doctor online to know details about medicines and other things.
4. Earning: We need money to reduce unwanted problems and you can use technology for this purpose. We can trade stocks, equities, bitcoins and other products online which will help generate more revenue. Be it stock trading or currency selling, there are various applications available for you to learn the basics easily. This, in turn, offers a way to significantly reduce risks and other problems. Internet technology enables you to earn more money through blogging, affiliate marketing, writing, publishing, videos and other sources.

_This is my first article on dev. I will try to write an article every week. Please inspire me by hit like and comment. _