public object Part2(IParsedFile file)
{
var adapters = file.ToList <int>();
adapters.Add(0);
adapters.Sort();
adapters.Add(adapters[^ 1] + 3);
public object Part1(IParsedFile file)
{
var numbers = file.ToList <int>();
var match = numbers.First(number => numbers.IndexOf(2020 - number) != -1);
return(match * (2020 - match));
}
public object Part2(IParsedFile file)
{
const ulong invalid = 375054920UL;
var numbers = file.ToList <string>().Select(ulong.Parse).ToArray();
var prefix = new BigInteger[numbers.Length];
prefix[0] = numbers[0];
for (int i = 1; i < numbers.Length; i++)
{
prefix[i] = prefix[i - 1] + numbers[i];
}
for (int i = 0; i < numbers.Length; i++)
{
for (int j = i + 1; j < numbers.Length; j++)
{
if (prefix[j] - prefix[i] == invalid)
{
var segment = numbers.Skip(i + 1).Take(j - i);
Debug.Assert(segment.Aggregate(0UL, (a, c) => a + c) == invalid);
return(segment.Min() + segment.Max());
}
}
}
return(null);
}
public object Part1(IParsedFile file)
{
var adapters = file.ToList <int>();
adapters.Add(adapters.Max() + 3);
adapters.Add(0);
adapters.Sort();
var enumer = adapters.Zip(adapters.Skip(1)).Select((x) => x.Second - x.First);
return(enumer.Count(x => x == 1) * enumer.Count(x => x == 3));
}
public object Part1(IParsedFile file)
{
var numbers = file.ToList <string>().Select(ulong.Parse).ToArray();
for (int i = 25; i < numbers.Length; i++)
{
var seg = new ArraySegment <ulong>(numbers, i - 25, 25);
if (GetSums(seg).All(x => x != numbers[i]))
{
return(numbers[i]);
}
}
throw new Exception();
}
public object Part2(IParsedFile file)
{
var numbers = file.ToList <int>();
for (int x = 0; x < numbers.Count; x++)
{
for (int y = x + 1; y < numbers.Count; y++)
{
for (int z = y + 1; z < numbers.Count; z++)
{
if (numbers[x] + numbers[y] + numbers[z] == 2020)
{
return(numbers[x] * numbers[y] * numbers[z]);
}
}
}
}
throw new Exception();
}
public object Part1(IParsedFile file)
{
string[] rows = file.ToList <string>().ToArray();
int x = 0, y = 0;
var count = 0;
while (y < rows.Length)
{
if (rows[y][x] == '#')
{
count++;
}
x += 3;
if (x >= rows[y].Length)
{
x %= rows[y].Length;
}
y++;
}
return(count);
}