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using System.IO;
using System.Linq;
namespace aoc2019
{
internal class Day4 : Day
{
public override int DayNumber => 4;
private readonly int start;
private readonly int end;
public Day4()
{
var range = File.ReadLines("input/day4.in")
.First().Split('-').Select(int.Parse).ToList();
start = range[0]; end = range[1];
}
private bool IsValid(int i)
{
int prev = 0; bool hasDup = false;
foreach (var c in i.ToString())
{
int curr = c - '0';
if (curr < prev) return false;
if (curr == prev) hasDup = true;
prev = curr;
}
return i >= start && i <= end && hasDup;
}
public override string Part1()
{
return $"{Enumerable.Range(start, end).Count(IsValid)}";
}
private bool HasOnePair(int i)
{
var s = i.ToString();
return IsValid(i) && s.Select(c => s.Count(j => j == c)).Any(c => c == 2);
}
public override string Part2()
{
return $"{Enumerable.Range(start,end).Count(HasOnePair)}";
}
}
}
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