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Day04.cs
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Day04.cs
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using System;
using AdventOfCode.CSharp.Common;
namespace AdventOfCode.CSharp.Y2020.Solvers;
public class Day04 : ISolver
{
public static void Solve(ReadOnlySpan<byte> input, Solution solution)
{
int part1 = 0;
int part2 = 0;
foreach (ReadOnlySpan<byte> passport in input.Split("\n\n"u8))
{
byte fieldFlags = 0;
bool hasInvalidField = false;
int i = 0;
while (i < passport.Length)
{
ReadOnlySpan<byte> fieldName = passport.Slice(i, 3);
int fieldLength = passport.Slice(i + 4).IndexOfAny("\n "u8);
if (fieldLength == -1)
{
fieldLength = passport.Length - i - 4;
}
ReadOnlySpan<byte> fieldValue = passport.Slice(i + 4, fieldLength);
switch (fieldName[0])
{
case (byte)'b': // byr
fieldFlags |= 1 << 0;
hasInvalidField = hasInvalidField || !IsValidBirthYear(fieldValue);
break;
case (byte)'i': // iyr
fieldFlags |= 1 << 1;
hasInvalidField = hasInvalidField || !IsValidIssueYear(fieldValue);
break;
case (byte)'e' when fieldName[1] == 'y': // eyr
fieldFlags |= 1 << 2;
hasInvalidField = hasInvalidField || !IsValidExpirationYear(fieldValue);
break;
case (byte)'h' when fieldName[1] == 'g': // hgt
fieldFlags |= 1 << 3;
hasInvalidField = hasInvalidField || !IsValidHeight(fieldValue);
break;
case (byte)'h': // hcl
fieldFlags |= 1 << 4;
hasInvalidField = hasInvalidField || !IsValidHairColour(fieldValue);
break;
case (byte)'e': // ecl
fieldFlags |= 1 << 5;
hasInvalidField = hasInvalidField || !IsValidEyeColour(fieldValue);
break;
case (byte)'p': // pid
fieldFlags |= 1 << 6;
hasInvalidField = hasInvalidField || !IsValidPassportId(fieldValue);
break;
}
i += 5 + fieldLength;
}
if (fieldFlags == 0b1111111)
{
part1 += 1;
if (!hasInvalidField)
{
part2 += 1;
}
}
}
solution.SubmitPart1(part1);
solution.SubmitPart2(part2);
}
public static bool IsValidBirthYear(ReadOnlySpan<byte> span)
{
if (span.Length != 4)
{
return false;
}
return span[0] switch
{
(byte)'1' => span[1] == '9' &&
span[2] is >= (byte)'2' and <= (byte)'9' &&
span[3] is >= (byte)'0' and <= (byte)'9',
(byte)'2' => span[1] == '0' &&
span[2] == '0' &&
span[3] is >= (byte)'0' and <= (byte)'2',
_ => false,
};
}
public static bool IsValidIssueYear(ReadOnlySpan<byte> span)
{
if (span.Length != 4 || span[0] != '2' || span[1] != '0')
{
return false;
}
return span[2] switch
{
(byte)'1' => span[3] is >= (byte)'0' and <= (byte)'9',
(byte)'2' => span[3] == '0',
_ => false,
};
}
public static bool IsValidExpirationYear(ReadOnlySpan<byte> span)
{
if (span.Length != 4 || span[0] != '2' || span[1] != '0')
{
return false;
}
return span[2] switch
{
(byte)'2' => span[3] is >= (byte)'0' and <= (byte)'9',
(byte)'3' => span[3] == '0',
_ => false,
};
}
public static bool IsValidHeight(ReadOnlySpan<byte> span)
{
switch (span.Length)
{
case 4: // inches
if (span[2] != 'i' || span[3] != 'n')
{
return false;
}
return span[0] switch
{
(byte)'5' => span[1] == '9',
(byte)'6' => span[1] is >= (byte)'0' and <= (byte)'9',
(byte)'7' => span[1] is >= (byte)'0' and <= (byte)'6',
_ => false
};
case 5: // centimetres
if (span[0] != '1' || span[3] != 'c' || span[4] != 'm')
{
return false;
}
return span[1] switch
{
(byte)'9' => span[2] is >= (byte)'0' and <= (byte)'6',
>= (byte)'5' => span[2] is >= (byte)'0' and <= (byte)'9',
_ => false
};
default:
return false;
}
}
public static bool IsValidHairColour(ReadOnlySpan<byte> span)
{
if (span.Length != 7 || span[0] != '#')
{
return false;
}
for (int i = 0; i < 6; i++)
{
if (span[i + 1] is not ((>= (byte)'0' and <= (byte)'9') or (>= (byte)'a' and <= (byte)'f')))
{
return false;
}
}
return true;
}
public static bool IsValidEyeColour(ReadOnlySpan<byte> span)
{
if (span.Length != 3)
{
return false;
}
return span[0] switch
{
(byte)'a' => span[1] == 'm' && span[2] == 'b',
(byte)'b' => span[1] switch { (byte)'l' => span[2] == 'u', (byte)'r' => span[2] == 'n', _ => false },
(byte)'g' => span[1] == 'r' && span[2] is (byte)'y' or (byte)'n',
(byte)'h' => span[1] == 'z' && span[2] == 'l',
(byte)'o' => span[1] == 't' && span[2] == 'h',
_ => false
};
}
public static bool IsValidPassportId(ReadOnlySpan<byte> span)
{
if (span.Length != 9)
{
return false;
}
for (int i = 0; i < 9; i++)
{
if (span[i] is not (>= (byte)'0' and <= (byte)'9'))
{
return false;
}
}
return true;
}
}