30 lines
768 B
C#
30 lines
768 B
C#
namespace AOC2020;
|
|
|
|
/// <summary>
|
|
/// Day 1: <see href="https://adventofcode.com/2020/day/1" />
|
|
/// </summary>
|
|
public sealed class Day01 : Day
|
|
{
|
|
private readonly ImmutableHashSet<int> _entries;
|
|
|
|
public Day01() : base(2020, 1, "Report Repair") =>
|
|
_entries = Input.Select(int.Parse).ToImmutableHashSet();
|
|
|
|
public override string Part1()
|
|
{
|
|
var entry = _entries.First(e => _entries.Contains(2020 - e));
|
|
return $"{entry * (2020 - entry)}";
|
|
}
|
|
|
|
public override string Part2()
|
|
{
|
|
foreach (var i in _entries)
|
|
foreach (var j in _entries)
|
|
foreach (var k in _entries)
|
|
if (i + j + k == 2020)
|
|
return $"{i * j * k}";
|
|
|
|
return "";
|
|
}
|
|
}
|