aannenko

var myDict = new NaiveDictionary<int, string?>();

myDict[1] = "abc";
myDict[1] = "def";
myDict[2] = "def";
myDict[3] = "def";
myDict[4] = "def";
myDict[5] = "def";
myDict[6] = "def";
myDict[7] = "def";

aannenko

GetPermutations(['a', 'b', 'c', 'd']).Dump();

static IEnumerable<string> GetPermutations(char[] chars)
{
    yield return new string(chars);

    if (chars.Length < 2)
        yield break;

    var counter = new int[chars.Length];

aannenko

char[] chars = ['a', 'b', 'c', 'd'];
GetPermutationsRecursive(chars.Length, chars).Dump();

static IEnumerable<string> GetPermutationsRecursive(int take, char[] chars)
{
    if (take is 1)
    {
        yield return new string(chars);
    }
    else

aannenko

// Given an array of distinct integer values, count the number of pairs of integers that 
// have difference k. For example, given the array [1, 7, 5, 9, 2, 12, 3] and the difference
// k = 2, there are four pairs with difference 2: (1, 3), (3, 5), (5, 7), (7, 9).

CountPairsWithDifference([1, 7, 5, 9, 2, 12, 3], 2).Dump(); // 4
CountPairsWithDifference([int.MaxValue, int.MinValue, int.MaxValue - 2, int.MinValue + 2], 2).Dump(); // 2
CountPairsWithDifference([1, 7, 5, 9, 2, 12, 3], 0).Dump(); // 0
CountPairsWithDifference([1, 7, 5, 9, 2, 12, 3], -2).Dump(); // 4

int CountPairsWithDifference(int[] integers, int diff)

aannenko

// Find all positive solutions to the equation a^3 + b^3 = c^3 + d^3
// where a, b, c, and d are integers between 1 and 1000.

FindCubicSumPairs(1, 1000).Dump();

static IEnumerable<(int A, int B, int C, int D)> FindCubicSumPairs(int min, int max)
{
    var sumToPairs = new Dictionary<double, List<(int, int)>>();
    for (int a = min; a <= max; a++)
    {

aannenko

// Given a smaller string "pattern" and a bigger string "text",
// design an algorithm to find all permutations of the shorter
// string within the longer one. Return the location of each permutation.

CountPermutations("cbabadcbbabbcbabaabccbabc", "abbc").Dump();
// Output: [0, 6, 9, 11, 12, 20, 21]

CountPermutations("encyclopedia", "dep").Dump();
// Output: [7]

aannenko

BenchmarkDotNet v0.14.0, Windows 11 (10.0.26100.2605)
13th Gen Intel Core i9-13900K, 1 CPU, 32 logical and 24 physical cores
.NET SDK 9.0.101
  [Host]     : .NET 9.0.0 (9.0.24.52809), X64 RyuJIT AVX2
  DefaultJob : .NET 9.0.0 (9.0.24.52809), X64 RyuJIT AVX2


| Method            | Mean      | Error     | StdDev    | Ratio | Gen0   | Gen1   | Allocated | Alloc Ratio |
|------------------ |----------:|----------:|----------:|------:|-------:|-------:|----------:|------------:|
| FindMagnetInLines | 24.945 μs | 0.2800 μs | 0.2619 μs |  1.00 | 4.1504 | 0.0610 |   78168 B |       1.000 |

aannenko

using Microsoft.AspNetCore.Routing.Constraints;
using System.Text.Json.Serialization;

var builder = WebApplication.CreateSlimBuilder(args);

builder.Services.ConfigureHttpJsonOptions(
    options => options.SerializerOptions.TypeInfoResolverChain.Insert(0, AppJsonSerializerContext.Default));

builder.Services.Configure<RouteOptions>(
    options => options.SetParameterPolicy<RegexInlineRouteConstraint>("regex"));

aannenko

namespace LibraryManager;

public sealed record Book(string Name, bool CanBeBorrowed, int? AgeRating) : ILibraryItem;

aannenko

Console.WriteLine(RotatedBinarySearch([6, 7, 8, 9, 10, 1, 2, 3, 5], 3)); // 7
Console.WriteLine(RotatedBinarySearch([1, 1, 1, 1, 1, 1, 2, 1, 1, 1], 2)); // 6

static int RotatedBinarySearch(int[] ints, int searchedValue)
{
    var low = 0;
    var high = ints.Length - 1;
    while (low <= high)
    {
        var mid = low + (high - low) / 2;