Math Problem on LC

-
This problem is a simple math one on Leetcode: Find Three Consecutive Integers That Sum to a Given Number - LeetCode

"Given an integer num, return three consecutive integers (as a sorted array) that sum to num. If num cannot be expressed as the sum of three consecutive integers, return an empty array."

Call the 3 consecutive numbers N, N+1 and N+2. Hence:

N+N+1+N+2 = num
3N+3 = num
N = (num-3)/3

With that, the solution becomes straightforward - one-liner:

return (num - 3) % 3 != 0 ? new long[] { } : new long[] { (num - 3) / 3, (num - 3) / 3 + 1, (num - 3) / 3 + 2 };

Cheers, ACC




Comments

Post a Comment

Popular posts from this blog

Advent of Code - Day 6, 2024: BFS and FSM

-
Image
To solve this Advent of Code (parts 1 and 2), I used Breadth-First Search (BFS) to keep moving the guard as well as Finite State Machine (FSM) to control the directions. This solves part 1 easily. Part 2 can be solved using the same technique, takes a little longer since you need to try every empty cell, but it eventually does the trick (takes a min or so). Code is down below, cheers, ACC. Day 6 - Advent of Code 2024 using System.IO; using System.Collections; using System; using System.Text; using System.Text.RegularExpressions; using System.ComponentModel.DataAnnotations; Process2(); void Process() { string fileName = "input.txt"; FileInfo fileInfo = new FileInfo(fileName); StreamReader sr = fileInfo.OpenText(); List map = new List (); int startRow = 0; int startCol = 0; while (!sr.EndOfStream) { string line = sr.ReadLine().Trim(); map.Add(new StringBuilder(line)); int indexStart = line.IndexOf('^'); ...
Read more

Golang vs. C#: performance characteristics (simple case study)

-
Image
This is an interesting example to study the performance characteristics of Golang compared to C# for a very particular case (not generalized though).  The same code was written in C# and Golang (literally translated from one to the other). Below you'll be able to see the source code for both. The problem is a simple post-order DFS in a tree-like graph. The code in C# times out (TLE = Time Limited Exceeded). The code in Golang not only works but beats 100% of the other Golang submissions. Take a look the image below: Some potential reasons for the performance gains from Go in this particular example are: 1. Language and Runtime Differences:    Go is compiled directly to machine code, while C# typically runs on a virtual machine (CLR).    Go has a simpler runtime with less overhead compared to the .NET runtime.    Go's garbage collector is designed for low latency, which can lead to better performance in some scenarios. 2. Data Structures:    G...
Read more

Advent of Code - Day 7, 2024: Backtracking and Eval

-
Image
Problem today requires backtracking and eval (evaluating a mathematical expression in the format of a string). Glad that it used a left-2-right evaluation, makes for an easy parsing and not overly complicated evaluation function. Code is down below for parts 1 and 2. Cheers, ACC. Day 7 - Advent of Code 2024 using System.IO; using System.Collections; using System; using System.Text; using System.Text.RegularExpressions; using System.ComponentModel.DataAnnotations; Process2(); void Process() { string fileName = "input.txt"; long retVal = 0; FileInfo fileInfo = new FileInfo(fileName); StreamReader sr = fileInfo.OpenText(); while (!sr.EndOfStream) { string line = sr.ReadLine().Trim(); string[] parts1 = line.Split(':'); long target = Int64.Parse(parts1[0]); string[] numbers = parts1[1].Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries); if (TryAll1(numbers, target, "", 0)) r...
Read more