## Largest Triple Product Third Post in Java

In this post we will revisit a practice question Largest Triple Products. Not sure if today this question would be of interest to Facebook and /or to Meta Platforms technical job seekers.

My original post Largest Triple Products was superseded by Largest Triple Products – Revisited and by this latest post.

The motivation for this post came from a question left by Brent Boyer which suggested an implementation for the function of interest. I have included it in this post as `findMaxProduct3`. Continue reading “Largest Triple Product Third Post in Java”

## LeetCode 295. Find Median from Data Stream in Java

In this post we will try to solve the LeetCode 295. Find Median from Data Stream problem using the Java programming language and the VSCode IDE on a Windows computer.

```The median is the middle value in an ordered integer list.
If the size of the list is even,
there is no middle value and the median is the mean of the two middle values.

For example, for arr = [2,3,4], the median is 3.
For example, for arr = [2,3], the median is (2 + 3) / 2 = 2.5.

Implement the MedianFinder class:

o MedianFinder()
initializes the MedianFinder object.
adds the integer num from the data stream to the data structure.
o double findMedian()
returns the median of all elements so far.

Constraints:

o -10^5 &lt;= num &lt;= 10^5
o There will be at least one element in the data structure before calling findMedian.
o At most 5 * 10^4 calls will be made to addNum and findMedian.

Related Topics:

o Two Pointers
o Design
o Sorting
* Heap (Priority Queue)
o Data Stream
```

In a nutshell the class needs to process integers in the specified range and at different points we can be asked to return the current Median. As a brute force approach, I tried sorting. I did not submit such an approach because it is quite expensive (slow) and the problem is rated Hard by LeetCode. Continue reading “LeetCode 295. Find Median from Data Stream in Java”

## LeetCode 307. Range Sum Query – Mutable in Java

In this post we will tackle the LeetCode 307. Range Sum Query – Mutable problem using the Java programming language and the VSCode IDE on a Windows computer. Unless you have a good reason (i.e., keep test code and solution on the same source code) my suggestion is to solve the problem using the online IDE provided by LeetCode.

```Given an integer array nums, handle multiple queries of the following types:

o Update the value of an element in nums.
o Calculate the sum of the elements of nums between indices left and right inclusive
where left <= right.

Implement the NumArray class:

o NumArray(int[] nums)
Initializes the object with the integer array nums.

o void update(int index, int val)
Updates the value of nums[index] to be val.

o int sumRange(int left, int right)
Returns the sum of the elements of nums between indices left and right inclusive (i.e. nums[left] + nums[left + 1] + ... + nums[right]).

Constraints:

o 1 <= nums.length <= 3 * 10^4
o -100 <= nums[i] <= 100
o 0 <= index < nums.length
o -100 <= val <= 100
o 0 <= left <= right < nums.length
o At most 3 * 10^4 calls will be made to update and sumRange.

Related Topics:

* Array
o Design
o Binary Indexed Tree
* Segment Tree
```

We are given an int[] and asked to perform two operations as part of a class. Continue reading “LeetCode 307. Range Sum Query – Mutable in Java”

## LeetCode 1504. Count Submatrices With All Ones in Java

In this post we will solve LeetCode 1504. Count Submatrices With All Ones problem using the Java programming language, the VSCode IDE on a Windows computer. My suggestion to you is that unless you have some special set of requirements, use the online IDE provided by LeetCode.

```Given an m x n binary matrix mat,
eturn the number of submatrices that have all ones.

Constraints:

o 1 <= m, n <= 150
o mat[i][j] is either 0 or 1.

Related Topics:

o Array
* Dynamic Programming
o Stack
o Matrix
o Monotonic Stack
```

In this problem we are provided a two dimensional matrix that only contains 1s and 0s. The dimensions are specified by `n` and `m`. Our mission if we wish to accept it, is to return the number of submatrices of 1s. Continue reading “LeetCode 1504. Count Submatrices With All Ones in Java”

## LeetCode 681. Next Closest Time in Java

In this post we will solve LeetCode 681. Next Closest Time problem using the Java programming language, the VSCode IDE on a Windows computer. Please note that the computer platform and the IDE should make no difference. One of the simplest ways to solve the problem is to use the online IDE provided by LeetCode.

```Given a time represented in the format "HH:MM",
form the next closest time by reusing the current digits.
There is no limit on how many times a digit can be reused.

You may assume the given input string is always valid.
For example, "01:34", "12:09" are all valid.
"1:34", "12:9" are all invalid.

Constraints:

* time.length == 5
* time is a valid time in the form "HH:MM".
o 0 <= HH < 24
o 0 <= MM < 60

Related Topics:

o String
o Enumeration
```

We are given a string with a time expressed in 24-hour format. By reusing the digits as many times as needed, we need to form the next closest time. Continue reading “LeetCode 681. Next Closest Time in Java”

## LeetCode 84. Largest Rectangle in Histogram in Java

In this post we will solve LeetCode 84. Largest Rectangle in Histogram problem using the Java programming language and the VSCode IDE on a Windows computer.

```Given an array of integers heights representing the histogram's bar height where the width of each bar is 1,
return the area of the largest rectangle in the histogram.

Constraints:

o 1 <= heights.length <= 10^5
o 0 <= heights[i] <= 10^4

Related Topics:
* Array
o Stack
* Monotonic Stack
```

We are given an array representing a histogram. The width of each bar holding a value is 1 unit. We are asked to return the area of the largest rectangle in the histogram. Continue reading “LeetCode 84. Largest Rectangle in Histogram in Java”

## LeetCode 1804. Implement Trie II (Prefix Tree) in Java

In this post I will solve LeetCode 1804. Implement Trie II (Prefix Tree) problem using Java and the VSCode IDE on a Windows computer.

In a previous post we discussed and implemented a solution for LeetCode 208. Implement Trie (Prefix Tree) in Java which is similar yet different to this one.

Please note that I carried away experimenting with the current problem as I did with the previous one. Due to this I implemented two solutions. After the first one was accepted I tried improving performance and readability. That created a second solution. Due to my approach I ended up with a large amount of code which I will post and comment on. For the first implementation I will go light on comments. Continue reading “LeetCode 1804. Implement Trie II (Prefix Tree) in Java”

## LeetCode 208. Implement Trie (Prefix Tree) in Java

In this post I will solve the LeetCode 208 Implement Trie (Prefix Tree) problem using the Java programming language and the VSCode IDE on a Windows computer. After the code was accepted by LeetCode I decided to add a couple features. The first one is to provide a method to access one of the main uses for a Trie (https://en.wikipedia.org/wiki/Trie). The second, which is based on the first one, is used to display, in order, the words inserted into the Trie.

```A trie (pronounced as "try") or prefix tree is a tree data structure
used to efficiently store and retrieve keys in a dataset of strings.
There are various applications of this data structure,
such as autocomplete and spellchecker.

Implement the Trie class:

* Trie()
Initializes the trie object.
* void insert(String word)
Inserts the string word into the trie.
* boolean search(String word)
Returns true if the string word is in the trie (i.e., was inserted before), and false otherwise.
* boolean startsWith(String prefix)
Returns true if there is a previously inserted string word that has the prefix prefix,
and false otherwise.

Constraints:

o 1 <= word.length, prefix.length <= 2000
o word and prefix consist only of lowercase English letters.
o At most 3 * 10^4 calls in total will be made to insert, search, and startsWith.

Related Topics:

o Hash Table
o String
o Design
o Trie
```

The requirements are very well described. We need to implement the class Trie which must include a specific set of methods. In addition we need to specify the class members. Continue reading “LeetCode 208. Implement Trie (Prefix Tree) in Java”

## LeetCode 760. Find Anagram Mappings in Java

In this post we will solve LeetCode 760. Find Anagram Mappings problem using the Java programming language.

```You are given two integer arrays nums1 and nums2 where nums2 is an anagram of nums1.
Both arrays may contain duplicates.

Return an index mapping array mapping from nums1 to nums2 where
mapping[i] = j means the ith element in nums1 appears in nums2 at index j.
If there are multiple answers, return any of them.

An array a is an anagram of an array b means b is made by randomizing the order of the elements in a.

Constraints:

o 1 <= nums1.length <= 100
o nums2.length == nums1.length
o 0 <= nums1[i], nums2[i] <= 10^5
o nums2 is an anagram of nums1.

Related Topics:

o Array
o Hash Table
```

We are provided with two int[] holding two anagrams. We need to write a function that returns an index mapping array mapping from nums1 to nums2 where mapping[i] = j means the ith element in nums1 appears in nums2 at index j. Continue reading “LeetCode 760. Find Anagram Mappings in Java”

## LeetCode 1518. Water Bottles in Java

In this post we will solve LeetCode 1518. Water Bottles problem using the Java programming language.

```There are numBottles water bottles that are initially full of water.
You can exchange numExchange empty water bottles from the market with one full water bottle.

The operation of drinking a full water bottle turns it into an empty bottle.

Given the two integers numBottles and numExchange,
return the maximum number of water bottles you can drink.

Constraints:

o 1 <= numBottles <= 100
o 2 <= numExchange <= 100

Related Topics:

o Math
o Simulation
```

Before you start solving a problem associated with a website make sure you read the current description directly from the site in order to get the current description of the problem. On occasions descriptions may be updated providing additional information that may help you come up with a better solution faster. Continue reading “LeetCode 1518. Water Bottles in Java”