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Posts Tagged: java

792. Number of Matching Subsequences

Given a string s and an array of strings words, return the number of words[i] that is a subsequence of s. A subsequence of a string is a new string generated from the original string with some characters (can be none) deleted without changing the relative order of the remaining characters...

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Testing Preauthorize Annotation in Spring Boot

Preauthorize annotation can be use to enforce access control in Spring Boot applications. It's part of Spring Security that allows you to specify access control expression for methods. These expressions are evaluated before method execution, determining whether the current user has the authority to invoke the method...

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Method Overloading and Varargs in Java

Method overloading is a fundamental concept in object-oriented programming that allows multiple methods to share the same name within a class, differentiated by their parameter lists. This feature enhances code readability and provides type safety at compile-time...

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Optimizing Builds with Gradle Build Cache

Gradle build cache is an essential tool for optimizing build times in software development. By storing build outputs either locally or remotely, it significantly reduces the time and resources required for rebuilding similar tasks. This cache mechanism is especially beneficial in continuous integration environments where builds occur frequently...

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Maximum Width of Binary Tree

The problem statement, as given on LeetCode, asks us to find the maximum width of a binary tree. The width of a level is defined as the number of nodes at that level. The maximum width of the binary tree is the maximum width among all levels...

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Binary Tree Right Side View Leetcode

We delve into a popular algorithmic problem from LeetCode: the "Binary Tree Right Side View". This problem is an excellent exercise for understanding tree-based data structures and breadth-first traversal techniques...

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Understanding Liskov Substitution Principle

The Liskov Substitution Principle, named after Barbara Liskov who introduced it in 1987, is one of the five SOLID principles of object-oriented design and programming. It states that..

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Understanding final vs Static final in Java

Java provides various modifiers to control the behavior of classes, methods, and variables. Two such modifiers are final and static final. Let's delve deeper into their significance and differences...

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Time Based Key-Value Store Solution

Design a time-based key-value data structure that can store multiple values for the same key at different time stamps and retrieve the key's value at a certain timestamp...

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Mastering Reactive Pagination with Spring Boot and MongoDB

As we delve into the realms of sophisticated data management, we will be harnessing the strengths of Spring Boot, the agility of MongoDB, and the responsiveness of reactive programming to implement an efficient pagination system. Pagination is a critical feature, instrumental in enhancing user experience and application performance. By the end of this guide, you'll have a deep understanding of reactive pagination, equipping you with the skills to manage large data sets with ease and proficiency. Let's get started...

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The number of Weak Characters in the Game

You are playing a game that contains multiple characters, and each of the characters has two main properties: attack and defense. You are given a 2D integer array properties where properties[i] = [attacki, defensei] represents the properties of the ith character in the game....

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House Robber Leetcode Solution

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent houses have security systems connected and it will automatically contact the police if two adjacent houses were broken into on the same night...

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Kata - Correct the Time String

In this [kata](https://www.codewars.com/kata/57873ab5e55533a2890000c7/), you are given a string that represents a time in the format "HH:MM:SS". The string may be in the wrong format, or it may be missing some characters. Your task is to correct the string so that it represents a valid time...

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TestContainers with Spring Boot

Testcontainers is a Java library that provides lightweight, disposable containers for running integration tests. It's a useful tool for testing applications that rely on external dependencies like databases or message queues...

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Cribsheet for String in Java

Strings are immutable in java. It's best to convert string to StringBuilder/StringBuffer so that it's memory efficient for string manipulation...

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Transforming a blocking method to a reactive one using Spring Reactor

Reactive programming is becoming increasingly popular in modern software development, and the use of reactive frameworks like Spring Reactor and RxJava is becoming more common. Reactive programming is an event-driven approach to programming that emphasizes asynchronous data streams, non-blocking I/O, and functional programming...

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Cribsheet for Set in Java

A set in Java is a collection that stores a unique set of elements. This means that there are no duplicates in a set. You can define set using HashSet, TreeSet, or LinkedHashSet...

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Find if Path Exists in Graph leetcode solution

It's a easy problem on Graph in leetcode to find if a path exist in graph...

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Serialize and Deserialize Binary Tree Leetcode solution

Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure...

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Apply Discount To Prices leetcode solution

A sentence is a string of single-space separated words where each word can contain digits, lowercase letters, and the dollar sign '$'. A word represents a price if it is a sequence of digits preceded by a dollar sign...

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Sort Characters By Frequency solution leetcode

Given a string s, sort it in decreasing order based on the frequency of the characters. The frequency of a character is the number of times it appears in the string...

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Minimum Consecutive Cards to Pick up solution leetcode

An interesting problem on leetcode to find minimum number of ways to pick up consecutive cards. We will start with a brute force algorithm that would exceed in time limit. Later we will improve upon this algorithm using hashmap...

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Leetcode - All Divisions With the Highest Score of a Binary Array

You are given a **0-indexed** binary array `nums` of length `n`. `nums` can be divided at index `i` (where `0 <= i <= n`) into two arrays (possibly empty) numsleft and numsright..

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Course Schedule Leetcode Solution

There are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1. You are given an array prerequisites where prerequisites[i] = [ai, bi] indicates that you must take course bi first if you want to take course ai...

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Remove-all-adjacent-duplicates-in-string-ii Solution

You are given a string s and an integer k, a k duplicate removal consists of choosing k adjacent and equal letters from s and removing them, causing the left and the right side of the deleted substring to concatenate together...

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Lowest Common Ancestor of a Binary Tree

Questions involving the binary tree data structure are very popular in tech interviews, and can be challenging and varied! A binary tree is a data structure consisting of a collection of nodes (starting at a root node), where each node consists of a value (data), together with a directed edges to at most two nodes (the "left child" and "right child"), with the additional conditions that no two edges point to the same node and no edge points to the root. I recently solved an interesting problem on binary tree...

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Ternary String solution Codeforces - 1354B

Ternary string is an interesting problem that could be solved using two pointers techniques. It's a convenient way to keep track of multiple indices. This helps in making decisions based on two values...

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Coin Change solution leetcode

It's one of the most popular questions on leetcode that seems very easy at first. Coin change is a classic dynamic programming problem. I will proceed with an obvious (albeit wrong) solution and subsequently proceed to an efficient correct solution...

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Maximum Subarray

There's an interesting problem I recently solved on leetcode based on dynamic programming. My Github repository contains list of all problems that I have solved. I often start with a brute force approach without fretting about time complexity. Later I try to improve my algorithm for a better efficient solution...

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Getting started with Graph Part 1

Graph are data structures made of vertices & edges. There are lots of interesting problems that can be solved using graphs. Part 1 covers the basic for creating a template for graph data structure...

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Recursively sort a array

I recently came across a simple telephonic interview problem. The problem was to sort an array recursively. But even numbers need to be placed before odd numbers. At first glance it was obvious that it was a simple case of implementation of merge sort...

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Three Sum Problem Leetcode Solution

Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero...

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