# Java

## How to ReImplement strStr() in Java

What we want to achieve Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. Example 1:… Read More »How to ReImplement strStr() in Java

## Third Maximum Number with Java

The challenge Given a non-empty array of integers, return the third maximum number in this array. If it does not exist, return the maximum number. The time complexity must… Read More »Third Maximum Number with Java

## First Unique Character in a String using Java

The challenge Given a string, find the first non-repeating character in it and return its index. If it doesn’t exist, return -1. Examples: s =… Read More »First Unique Character in a String using Java

## How to Reverse an Integer in Java

The challenge Given a 32-bit signed integer, reverse digits of an integer. Example 1: Input: 123 Output: 321 Example 2: Input: -123 Output: -321 Example… Read More »How to Reverse an Integer in Java

## Reverse a String in-place using Java

The challenge Write a function that reverses a string. The input string is given as an array of characters char[]. Do not allocate extra space for… Read More »Reverse a String in-place using Java

## Check if a Java array Contains Duplicates

The challenge Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least… Read More »Check if a Java array Contains Duplicates

## The Array Height Checker Problem in Java

The challenge Students are asked to stand in non-decreasing order of heights for an annual photo. Return the minimum number of students that must move… Read More »The Array Height Checker Problem in Java

## Find the Squares of a Sorted Array in Java

The challenge Given an array of integers A sorted in non-decreasing order, return an array of the squares of each number, also in sorted non-decreasing order. Example 1: Input:… Read More »Find the Squares of a Sorted Array in Java

## Sorting a Java Array by Parity

The challenge Given an array A of non-negative integers, return an array consisting of all the even elements of A, followed by all the odd elements of A. You… Read More »Sorting a Java Array by Parity

## Remove Duplicates from Sorted Array in Java

Say you have an array of primitive integers and you want to remove all duplicates. You can find out how many non-duplicate integers are in… Read More »Remove Duplicates from Sorted Array in Java

## The Valid Mountain Array Problem using Java

Introducing the problem Given an array A of integers, return true if and only if it is a valid mountain array. Recall that A is a mountain array if and… Read More »The Valid Mountain Array Problem using Java

## Find Numbers with Even Number of Digits using Java

The challenge Given an array nums of integers, return how many of them contain an even number of digits. Example 1: Input: nums = [12,345,2,6,7896] Output: 2 Explanation: 12… Read More »Find Numbers with Even Number of Digits using Java

## How to use a Java HashSet by example

What is a HashSet A HashSet is an unordered collection containing unique elements. It has the standard collection operations Add, Remove, Contains, but since it… Read More »How to use a Java HashSet by example

## The Decoded String at Index using Java

The Challenge An encoded string S is given.  To find and write the decoded string to a tape, the encoded string is read one character at a time and the following… Read More »The Decoded String at Index using Java

## Find the Minimum Absolute Difference in BST using Java

The question Given a binary search tree with non-negative values, find the minimum absolute difference between values of any two nodes. Example: Input: 1 \ 3 /… Read More »Find the Minimum Absolute Difference in BST using Java

## Find Maximum Subarrays using Java

The problem Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum. Example: Input:… Read More »Find Maximum Subarrays using Java

## Finding Number Complements using Java

The problem Given a positive integer num, output its complement number. The complement strategy is to flip the bits of its binary representation. Example 1: Input: num =… Read More »Finding Number Complements using Java

## Comparing Java and Javascript

Perhaps the first thing that most people ask when they hear the names of these two programming languages are. “Why do they have the same… Read More »Comparing Java and Javascript

## The Primary Data Types in Java

In Java there are eight basic data types; which are: byte, short, int, long, float, double, boolean and char. It could realistically be said that… Read More »The Primary Data Types in Java

## Comparing Objects in Java

TLDR; Java has a few different ways of comparing variables and objects with one another. ==, equals(), compareTo() and compare(). Java provides various operators such… Read More »Comparing Objects in Java

## Overloading Operators in Java

As with many programming languages such as C, C++ and C# (known commonly as the C family), it is possible to “overload methods” (sometimes called… Read More »Overloading Operators in Java

## How to get the Range Sum of Binary Search Tree using Java

Given the root node of a binary search tree, return the sum of values of all nodes with value between L and R (inclusive). The binary search tree is guaranteed to… Read More »How to get the Range Sum of Binary Search Tree using Java

## Mocha Java Decompiler Download

Mocha is a Java Decompiler and is 100% FREE to use. The readme.txt file in the Mocha distribution offers the free usage license: The distribution… Read More »Mocha Java Decompiler Download