Reverse Linked List

In this post I will reverse a linked list in Java. As I mentioned in a previous post, I am in the process of refreshing recursion using Java. In the next few days I will pick up a few more problems and post my approach.

In this post I will deal with 206. Reverse Linked List. If interested please take a look at the requirements for the problem and then give it a try before looking at solutions. Continue reading “Reverse Linked List”

Number of Recent Calls

It is an ugly rainy and stormy day in the Twin Cities of Minneapolis and St. Paul.  It seems like the storms will resume around 03:00 PM later today. In general I shutdown all my desktop computers when there are thunderstorms. I have a couple UPS units but I have also invested time installing software and configuring them exactly the way I like it. Do not wish to change disks or re install software.

Earlier today I opened the LeetCode web site and selected the problems icon. In the search box I entered the word “recursion”. Many problems were listed. I sorted them by difficulty Easy to Difficult. I then selected problem 933. Number of Recent Calls. Time permitting, decided to tackle three problems in the three categories in the next few days. Continue reading “Number of Recent Calls”

Longest Univalue Path

I have a childhood best friend which we both attended K-12 in the same sequence of schools. We used to hang out on weekends and in some occasions would go out with the family. After high school we both went in different directions. We lost track of each other while attending college. A few years went by and we reconnected. Since then we have visited in person and our spouses appear to have connected well.

Through the years we kept in touch about once a month via Skype. Since the COVID-19 pandemic started, we talk once a week, typically on Friday. We are both morning people so we set the call time between 06:00 AM and 07:00 AM. This morning around 05:00 AM I received a message via Gmail that he had some work appointments early morning. We skipped the call but will reconnect next week. Continue reading “Longest Univalue Path”

Lowest Common Ancestor of a Binary Tree

Things might be getting somewhat more complex with the COVID-19 pandemic that started in Wuhan, China. The CDC has been posting articles stating that individuals, who have recovered from COVID-19, may be prone to reinfection after three months. The theory of herd immunity, without a vaccine, goes out the door.

On a side note, people in the city of Wuhan, China have been celebrating that coronavirus is receding (there is no way to find out with data what is actually happening there) in their city with a massive water park party. The Chinese Communist Party does not seem to accept responsibility for the 800,000 deaths globally which they allowed to happen and are taking advantage of it in different ways. Continue reading “Lowest Common Ancestor of a Binary Tree”

Lowest Common Ancestor in Binary Search Tree

It is a beautiful sunny summer day in the Twin Cities of Minneapolis and St. Paul. The high temperature for today in the city I live is forecasted to be 83 F. I prefer high temperatures in the range of 75 F to 80 F, but 83 F will have to do.

Yesterday I spent a few hours in front of my computers. My wife left early with a friend to go walking and shopping. My wife got back shortly after 11:00 AM. We made some potatoes with veggies in the grill using a cast iron pan. We always add some pepper, salt and a splash of oil with a high smoke point (i.e., avocado or peanut). Continue reading “Lowest Common Ancestor in Binary Search Tree”

Greatest Common Denominator

Last weekend my wife and I visited our son and family who live in Madison, Wisconsin. They like to cook and bake like we do. When I was growing up, most summer days I would make ice cream. The techniques and ingredients were quite simple.

Over the weekend my son made ice cream. He did it using the ice cream bowl for the Kitchenaid mixer. It happens that we also have an ice cream bowl. When we got back, we decided to make some ice cream using the same recipe that our son had used. We searched for our ice cream bowl which we have not used in years, but were not able to find it. We decided to use a regular bowl and the standard 6-wire whip attachment. Continue reading “Greatest Common Denominator”

Components in a Graph

It is a cloudy day in the Twin Cities of Minneapolis and St. Paul. Today I woke up around 05:00 AM. Read for about 45 minutes and then headed to the kitchen to prepare breakfast.

It is all over the news that most (never say all) states have started updating the stay home orders in order to give people more freedom to do the things we are used to. I fully agree that the economy needs to get back to what it was before the COVID-19 pandemic started. That said, we need to move slowly making sure that there are enough ICU beds for all people that requires them. If such quotas cannot be met, then we need to go back to a full quarantine. This type of cycle is well known and will come in the form of multiple waves.

In particular, in the State of Minnesota, the Mall of America and casinos (e.g., Mystic Lake Casino) are opening. My wife and I do not go to casinos. During the long winter months we go to the Mall of America early mornings before stores open to walk. At that time there are very few people. When we shop at the mall we visit Nordstrom and Macy’s.

Continue reading “Components in a Graph”

Disjoint Union Sets

It is a rainy Sunday morning in the Twin Cities of Minneapolis and St. Paul. Rain started last evening around 08:00 PM and according to the weather forecast will subside later tonight around 10:00 PM. Not a nice day to be outdoors or grilling.

Last Friday my son mentioned that he would be going shopping on Saturday morning to the Costco Minneapolis Business Center Warehouse. My wife and I decided to join him at 07:00 AM (opening time). We met in the parking lot, donned our gloves and mask, and headed in. We have been at the Restaurant Depot many times, but were nicely surprised with the size of the Costco facility and the variety of items. From now on my wife and I will make the trip from home (30 minutes about 20 miles away) a couple times a month to the Costco in Minneapolis. We believe it is worth the drive.

My wife and I cook and bake. I like to bake deserts, breads and Italian cuisine. My wife cooks lunch during the workdays. We both cook on weekends. We have breakfast which I prepare every day and we both skip dinner. The point that I am trying to make is that we did not start cooking or baking due to the coronavirus pandemic.

Last week we noticed that we were running very low on yeast. We went grocery shopping last Tuesday morning and where not able to find yeast at Costco in Eagan, MN or Trader Joe’s in St. Paul. Back home, I went to Amazon.com and ordered a 2 pound pouch of Red Star dry yeast. The total after taxes (we do have Amazon Prime) came to $24.99 USD. I thought it was expensive but it seems that every one and their brother are baking now a day. The delivery will be sometime tomorrow (Monday).

While at Costco we found lots of Red Star dry yeast in the same 2 lb pouches we ordered from Amazon. That is the same yeast we have been using for over a decade. What we found disgusting was that Costco had the same 2 lb pouches of yeast for under $4.50 USD each. We bought two pouches (totaling 4 lbs) for about $9.00 USD. They should last a year or so. Continue reading “Disjoint Union Sets”

Down to Zero – Revisited

!!! NOTE !!!

Not sure what happens with the formatted code which seems to display well and sometimes it does not. The good thing is that the entire code is in my GitHub repository. Sorry about the inconvenience. If you have a formatter for Word Press that you like and is reliable, please let me know.

I received a message from a reader of my blog requesting some clarification on my original solution and associated post Down to Zero II. The associated post was from 2016. The initial code was not in my GitHub repository. Sorry about that.

After reading the message (which I keep private unless told otherwise) I went to GitHub and created a new repository. I added a short and simple README.md file and cloned the repo to one of my Windows 10 computers.

I then copied the original solution.java file and opened it using VSCode. The original code was developed using the Eclipse IDE. In the past year or so I have switched to VSCode for C++, Java, and Python. Continue reading “Down to Zero – Revisited”

Robot in a Grid

This past weekend my wife and I spent time looking for protein-rich groceries. We were attempting to get those and additional items for a few families that wish to stay in lockdown despite the governor of Minnesota starting to relax the lockdown. The current orders went into effect last Saturday April 18, 2020 at midnight. Among the main items is that people in the state can go golfing and shooting in open ranges. Both Saturday and Sunday were sunny days. We could tell for the number of cars and people walking the dogs, jogging and just strolling that many people took advantage of the new rules.

On our side we will continue to try stay home as much as we can by limiting trips to the grocery stores and continue to use Jitsi to communicate more often with family and friends. Continue reading “Robot in a Grid”