Leet Code Problems

  Adding Binary Numbers with JavaScript: A Step-by-Step Guide Adding binary numbers is a fundamental task in computer science, often encountered in various coding challenges and real-world applications. In this blog post, we will explore how to add binary numbers using JavaScript. We'll break down the problem, understand the approach, and provide a solution along with its complexity analysis. The Problem Statement Given two binary numbers represented as strings, the goal is to add these numbers and return their sum, also as a binary string. For instance, if the inputs are "1010" and "1011", the output should be "10101". Intuition The core idea behind this problem is similar to adding decimal numbers, but instead, we deal with binary digits (0 and 1). We need to handle the carry for each bit addition, which is crucial in binary arithmetic. Approach Let's break down our approach step by step: Initialize Variables : carry : This will hold the carryove...

Understanding and Implementing the Reverse Integer Problem In the world of algorithms and coding challenges, the reverse integer problem is a classic one. Whether you're preparing for coding interviews or just looking to improve your problem-solving skills, this problem offers a good mix of logic, string manipulation, and handling edge cases. Let's dive into understanding and implementing the solution for this problem. The Problem Statement Given a 32-bit signed integer, you need to reverse the digits of the integer. For example, if the input is 123 , the output should be 321 . If the input is -123 , the output should be -321 . Additionally, you must handle cases where the reversed integer might overflow beyond the 32-bit signed integer range. Intuition The core intuition behind solving this problem is straightforward: Convert the integer to its string representation. Reverse the string. Convert the reversed string back to an integer. Restore the sign if necessary. Ensure the r...

  Simplifying the Addition of Two Numbers Represented by Linked Lists In the world of coding and algorithms, one interesting problem is adding two numbers represented by linked lists. This classic problem often appears in technical interviews and helps in understanding linked lists and basic arithmetic operations. Today, we'll dive deep into solving this problem using JavaScript. Problem Description Given two non-empty linked lists representing two non-negative integers, the digits are stored in reverse order, and each node contains a single digit. Add the two numbers and return the sum as a linked list. Assume the two numbers do not contain any leading zeros, except the number 0 itself. Intuition To solve this problem, we can visualize adding the two numbers digit by digit, starting from the least significant digit (the head of the linked lists). The challenge involves handling the carry from each addition and constructing the resulting linked list accordingly. Approach Initialize...

  Mastering the Longest Substring Without Repeating Characters Problem Using Sliding Window and Set Introduction Welcome to another deep dive into solving classic algorithm problems! Today, we’re tackling the Longest Substring Without Repeating Characters problem. This is a common problem that tests your understanding of data structures and algorithmic techniques. We’ll explore an efficient solution using the sliding window technique combined with a Set. This approach is both intuitive and powerful, enabling us to solve the problem efficiently. Problem Description Given a string s , find the length of the longest substring without repeating characters. Essentially, we need to find the maximum length of a substring where no characters repeat. Intuition To solve this problem, we need to maintain a window (substring) where all characters are unique. The sliding window technique allows us to dynamically adjust the size of this window and ensure it contains only unique characters. We u...

  Mastering the Minimum Size Subarray Sum Problem with the Sliding Window Technique In this blog post, we’ll dive into a classic algorithm problem known as the Minimum Size Subarray Sum . This problem challenges us to find the minimal length of a contiguous subarray in a given array, where the sum is at least equal to a specified target. We’ll explore an efficient solution using the sliding window technique, and discuss the intuition, approach, and complexity analysis. Problem Description Given an array of positive integers nums and a positive integer target , find the minimal length of a contiguous subarray [nums[l], nums[l+1], ..., nums[r-1], nums[r]] of which the sum is greater than or equal to target . If there is no such subarray, return 0 instead. Intuition The challenge is to find a contiguous subarray whose sum is at least target and has the smallest possible length. Using a brute force approach to check all possible subarrays would be inefficient, especially for large a...

  Finding All Unique Triplets in an Array with Zero Sum Problem Description Given an integer array nums , our goal is to return all unique triplets [nums[i], nums[j], nums[k]] such that i != j , i != k , and j != k , and nums[i] + nums[j] + nums[k] == 0 . Intuition To solve this problem, we need to find triplets in the array that sum up to zero. By sorting the array first, we can efficiently find these triplets using a two-pointer technique. Sorting the array also helps us easily skip duplicate elements and manage indices better. Approach Initial Check : If the array has fewer than 3 elements, return an empty list as no triplet can be formed. Sorting : Sort the array in non-decreasing order, which helps in managing duplicates and using the two-pointer approach. Iterate and Find Triplets : Use a for-loop to iterate through the array, treating each element as the potential start of a triplet. For each element, use two pointers ( startIndex and endIndex ) to find pairs that, along w...

  Maximizing Water Containment with the Two-Pointer Technique in JavaScript The "Container With Most Water" problem on LeetCode is an intriguing challenge that asks us to find the two lines in a given array that, together with the x-axis, form a container holding the most water. This post will explore an efficient and elegant solution using the two-pointer technique in JavaScript. Problem Statement Given an array height of length n , where height[i] is the height of a vertical line at index i , find two lines that, together with the x-axis, form a container that holds the most water. Example Input : height = [1,8,6,2,5,4,8,3,7] Output : 49 Intuition The key to solving this problem efficiently lies in leveraging the fact that the array is sorted. By using two pointers—one starting at the beginning and one at the end of the array—we can systematically find the maximum area by moving the pointers inward based on the heights they point to. Approach Initialize Variables : Sta...

  Solving the Two Sum II Problem with a Two-Pointer Technique in JavaScript When faced with the task of finding two numbers in a sorted array that sum up to a specific target, the Two Sum II problem on LeetCode provides a classic challenge. In this post, we'll explore an efficient and elegant solution using the two-pointer technique in JavaScript. This approach ensures that we find the solution in linear time. Problem Statement Given an array of integers numbers that is already sorted in non-decreasing order, find two numbers such that they add up to a specific target number. Return the indices of the two numbers (1-based index) as an integer array [index1, index2] . You may assume that each input would have exactly one solution, and you may not use the same element twice. Example Input : numbers = [2, 7, 11, 15], target = 9 Output : [1, 2] Intuition Since the array is sorted, we can efficiently find the two numbers using the two-pointer technique. This method involves initial...

  Building an Efficient Subsequence Checker in JavaScript When working with strings, one common task is to determine if one string is a subsequence of another. A subsequence maintains the relative order of characters but does not require them to be contiguous. In this blog post, we'll walk through an efficient implementation of a subsequence checker in JavaScript. Problem Statement Given two strings s and t , the goal is to determine if s is a subsequence of t . A subsequence of a string is formed by deleting some (or no) characters from the string without changing the order of the remaining characters. Example Input : s = "abc", t = "ahbgdc" Output : true Input : s = "axc", t = "ahbgdc" Output : false Intuition To determine if s is a subsequence of t , we need to verify if the characters in s appear in t in the same order. This can be achieved using a simple iteration approach combined with a stack-like behavior. Approach Convert s to ...

  How to Check if a String is a Palindrome in JavaScript: A Step-by-Step Guide Palindromes are fascinating! Whether it's the word "racecar" or the phrase "A man, a plan, a canal, Panama," there's something intriguing about a sequence that reads the same backward and forward. If you’re looking to check if a string is a palindrome using JavaScript, you’re in the right place. Let's break down a simple approach to do just that. What is a Palindrome? A palindrome is a string that reads the same backward as forward. When checking for palindromes, we often ignore non-alphanumeric characters (like punctuation and spaces) and case differences. This means "A man, a plan, a canal: Panama" is considered a palindrome. Problem Statement Given a string s , determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. Return true if it is a palindrome, or false otherwise. Step-by-Step Approach Clean the String : Remove all no...

  Reversing Words in a String Using JavaScript Introduction Reversing the order of words in a string is a common problem in programming, often encountered in coding interviews and competitive programming. It involves manipulating strings and arrays to achieve the desired result efficiently. In this blog post, we'll explore how to reverse the words in a string using JavaScript. We'll break down the approach, understand the logic, and analyze the complexity of our solution. Problem Statement Given a string s , reverse the order of words in the string. A word is defined as a sequence of non-space characters. The words in s will be separated by at least one space. Intuition To reverse the order of words in a string, we need to: Split the string into individual words. Remove any extra spaces that may exist between the words. Reverse the order of the words. Join the words back into a single string. By breaking the problem down into these steps, we can effectively reverse the order o...