Learnitweb

Author: Editorial Team

  • LeetCode 993: Cousins in Binary Tree

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    Problem Statement Given a binary tree and two integers x and y, determine if the nodes with values x and y are cousins. Definition of cousins: Example 1: Example 2: Constraints: Approach to Solve the Problem (Simple Language) We need to check two conditions for nodes x and y: Steps: Why DFS works: Java Code…

  • LeetCode 169: Majority Element

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    Problem Statement Given an array nums of size n, find the majority element. The majority element is the element that appears more than ⌊n / 2⌋ times. You can assume that the majority element always exists in the array. Example 1: Example 2: Constraints: Approach to Solve the Problem (Simple Language) There are multiple ways…

  • LeetCode 387: First Unique Character in a String

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    Problem Statement Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1. Example 1: Example 2: Constraints: Approach (HashMap for General Characters) Advantages: Java Code Solution (HashMap) Dry Run Example Input: Step-by-step Execution: Index Char Count Is Unique? 0 a 2 No 1…

  • LeetCode 476: Number Complement

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    Problem Statement Given a positive integer num, find its complement. The complement of an integer is defined as flipping all the bits in its binary representation (0 → 1, 1 → 0). Example: Constraints: Approach to Solve the Problem (Simple Language) Why XOR works: Java Code Solution Dry Run Example Input: Step-by-step Execution: Textual Diagram…

  • LeetCode 383: Ransom Note

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    Problem Statement You are given two strings: You need to check if you can construct the ransomNote using the letters from magazine. Each letter in magazine can only be used once. Example: Constraints: Approach to Solve the Problem (Simple Language) Optimized Idea: Steps in short: Java Code Solution Dry Run Example Input: Step-by-step Execution: Array…

  • LeetCode 771: Jewels and Stones

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    Problem Statement You are given two strings: You want to know how many of the stones you have are also jewels. Example: Constraints: Approach to Solve the Problem (Simple Language) Optimized idea: Steps in short: This approach ensures fast lookup and is simple to understand. Java Code Solution Dry Run Example Input: Step-by-step execution: Stone…

  • What is technical debt?

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    Technical debt is a concept in software engineering that describes the cost of choosing a quick, easy, or suboptimal solution now instead of a better, cleaner, and more maintainable solution that would take longer to implement. Over time, this “debt” must be “repaid” with extra effort to fix bugs, refactor code, or improve performance and…

  • Implementing LRU Cache in Java

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    Caching is one of the most essential techniques for improving performance in systems that require fast access to frequently used data. An LRU (Least Recently Used) Cache is a type of cache algorithm that evicts the least recently used items first when the cache reaches its maximum capacity. In this tutorial, we’ll cover: 1. What…

  • Difference Between CascadeType.ALL and orphanRemoval in JPA/Hibernate

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    When we work with entity relationships in JPA (like @OneToMany, @OneToOne, @ManyToOne, etc.), two important features come into play to manage entity lifecycle propagation and child deletion: Although they may seem similar because both can trigger child deletions, their behavior and purpose are quite different. 1. What is CascadeType.ALL? CascadeType.ALL is a lifecycle propagation rule.It…

  • Shallow Copy vs Deep Copy in Java

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    In Java, copying an object is a common operation, especially when working with mutable classes, collections, or when implementing features like cloning, caching, or undo mechanisms. However, not all copies are the same. The way objects are copied determines whether the new object shares the same references or gets completely independent copies of its data.…