Docs.python.org

The Event Loop

The event loop contains a collection of jobs to be run. Some jobs are added by application code, and others indirectly by asyncio. The event loop takes a job from its backlog and invokes it (“gives it control”). Once that job pauses or completes, it returns control to the event loop which then selects another job from the backlog and invokes it. When there are no jobs to be done, the event loop rests (doesn’t waster CPU cycles) and comes back when more jobs are enqueued.

#intervals-algorithms

Merge Overlapping Intervals

Problem Statement: Merge Overlapping Intervals

Given an integer array intervals where intervals[i] = [start_i, end_i], merge all overlapping intervals and return an array of the non-overlapping intervals. For example \([[1,3],[2,6],[8,10],[15,18]] \to [[1,6],[8,10],[15,18]]\) because \([1,3]\) and \([2,6]\) overlap and merge into \([1,6]\).

Solution: Sort by Start Time and then Linear Scan

Like Minimum Size Subarray Sum , contiguity hints at a linear scan being useful. If we sort intervals by start, then it’s a matter of starting at some intervals[i] and expanding until some intervals[j], \(j > i\) is no longer overlapping.

Introduction

Threads are smaller units of a process that allow executing tasks in parallel, sharing memory space. Threads are particularly useful for I/O bound tasks, where much of the time is spent waiting for external resources.

Parsing

Each line represents a single equation, e.g., 292: 11 6 16 20.

Part One needs to make a decision based on each line independently. Parsing each line into a data structure and yielding that should suffice.

using System.Collections.Immutable;
using System.Text.RegularExpressions;

namespace AoC2024;

public partial class BridgeRepair
{
    public static IEnumerable<CalibrationEquation> Parse(string filePath)
    {
        using var inputReader = new StreamReader(filePath);

        string? line;
        while ((line = inputReader.ReadLine()) != null)
        {
            var numbers = InputLineRegex.Matches(line)
                .Select(match => long.Parse(match.Value));
            yield return new(numbers.First(), numbers.Skip(1).ToImmutableList());
        }
    }

    public readonly record struct CalibrationEquation(
        long Result, ImmutableList<long> Operands);

    private static Regex InputLineRegex = NumbersRegex();

    [GeneratedRegex(@"\d+")]
    static private partial Regex NumbersRegex();
}

Part One

Using only add and multiply, evaluated left-to-right (not according to math precedence rules), determine which equations could possibly be true. For example, \(292 = ((11 + 6) \times 16) + 20\). Of the equations that could possibly be true, what is the sum of their results?

#23 Non-abundant sums - Project Euler. projecteuler.net . Accessed Feb 19, 2023.

Problem Statement

A perfect number is a number for which the sum of its proper divisors is exactly equal to the number. For example, the sum of the proper divisors of \(28\) would be \(1 + 2 + 4 + 7 + 14 = 28\), which means that \(28\) is a perfect number.