public PairNumber(SnailfishNumber left, SnailfishNumber right)
{
Left = left;
Right = right;
left.Parent = this;
right.Parent = this;
}
SnailfishNumber ParseArray(ReadOnlySpan <char> line)
{
var number = new SnailfishNumber();
var start = number;
foreach (var c in line)
{
if (c == '[')
{
number.X = new SnailfishNumber
{
Parent = number
};
number.Y = new SnailfishNumber
{
Parent = number
};
number = number.X;
}
else if (c == ']')
{
number = number !.Parent !;
}
else if (c == ',')
{
number = number !.Parent !.Y !;
}
else
{
number.Value = c - '0';
}
}
return(start);
}
public void Part1()
{
SnailfishNumber number = ReadNumbersFromFile().Aggregate((left, right) => SnailfishNumber.Add(left, right));
int result = number.ComputeMagnitude();
Assert.Equal(3216, result);
}
internal SnailfishNumber Clone(SnailfishNumber parent = null)
{
SnailfishNumber number = new SnailfishNumber();
number.Value = Value;
number.Left = Left?.Clone(number);
number.Right = Right?.Clone(number);
number.Parent = parent;
return(number);
}
internal static SnailfishNumber Add(SnailfishNumber left, SnailfishNumber right)
{
if (left.Parent != null || right.Parent != null)
{
throw new Exception();
}
SnailfishNumber result = new SnailfishNumber();
result.Left = left;
result.Right = right;
left.Parent = result;
right.Parent = result;
result.Reduce();
return(result);
}
public void Part2()
{
int maxMagnitude = 0;
List <SnailfishNumber> numbers = ReadNumbersFromFile();
foreach (SnailfishNumber n1 in numbers)
{
foreach (SnailfishNumber n2 in numbers)
{
if (n1 != n2)
{
int magnitude = SnailfishNumber.Add(n1.Clone(), n2.Clone()).ComputeMagnitude();
maxMagnitude = Math.Max(maxMagnitude, magnitude);
}
}
}
Assert.Equal(4643, maxMagnitude);
}
internal static SnailfishNumber Parse(string input, SnailfishNumber parent = null)
{
if (input.StartsWith('['))
{
(string left, string right) = GetComponents(input.Substring(1, input.Length - 2));
SnailfishNumber number = new SnailfishNumber();
number.Left = Parse(left, number);
number.Right = Parse(right, number);
number.Parent = parent;
return(number);
}
return(new SnailfishNumber()
{
Value = int.Parse(input),
Parent = parent,
});
}
private SnailfishNumber GetNextNumber(SnailfishNumber requestingChild)
{
if (requestingChild == Right)
{
return((Parent != null) ? Parent.GetNextNumber(this) : null);
}
if (requestingChild == Left)
{
SnailfishNumber next = Right;
while (next.Value == null)
{
next = next.Left;
}
return(next);
}
throw new Exception();
}
private bool Explode(int depth = 0)
{
if (Value == null)
{
if (Left.Explode(depth + 1))
{
return(true);
}
if (depth >= 4 && Left.Value != null && Right.Value != null)
{
SnailfishNumber previous = Parent.GetPreviousNumber(this);
if (previous != null)
{
previous.Value += Left.Value;
}
SnailfishNumber next = Parent.GetNextNumber(this);
if (next != null)
{
next.Value += Right.Value;
}
Left = null;
Right = null;
Value = 0;
return(true);
}
if (Right.Explode(depth + 1))
{
return(true);
}
}
return(false);
}
private bool Split()
{
if (Value == null)
{
if (Left.Split())
{
return(true);
}
if (Right.Split())
{
return(true);
}
}
else if (Value.Value >= 10)
{
int mod = Value.Value % 2;
int div = Value.Value / 2;
Left = new SnailfishNumber()
{
Value = div,
Parent = this,
};
Right = new SnailfishNumber()
{
Value = div + mod,
Parent = this,
};
Value = null;
return(true);
}
return(false);
}
public static SnailfishNumber operator +(SnailfishNumber a, SnailfishNumber b)
{
var newNumber = new SnailfishNumber
{
X = a,
Y = b,
};
newNumber.X !.Parent = newNumber;
newNumber.Y !.Parent = newNumber;
#if DEBUG
Console.WriteLine($"after addition: {newNumber}");
#endif
while (true)
{
if (newNumber.Explode())
{
#if DEBUG
Console.WriteLine($"after explode: {newNumber}");
#endif
continue;
}
if (!newNumber.Split())
{
break;
}
#if DEBUG
Console.WriteLine($"after split: {newNumber}");
#endif
}
return(newNumber);
}
public void Snailfish_Magnitude(string input, int expected)
{
int actual = new SnailfishNumber(input).Magnitude;
Assert.Equal(expected, actual);
}
public void Snailfish_Explode(string input, string expected)
{
string actual = SnailfishNumber.Explode(input);
Assert.Equal(expected, actual);
}
public void Snailfish_Addition(string lho, string rho, string expected)
{
SnailfishNumber actual = new SnailfishNumber(lho) + new SnailfishNumber(rho);
Assert.Equal(expected, actual.Number);
}
private List <SnailfishNumber> ReadNumbersFromFile()
{
return(File.ReadAllLines("Day18Input.txt")
.Select(line => SnailfishNumber.Parse(line))
.ToList());
}
public Pair(SnailfishNumber left, SnailfishNumber right)
{
Left = left;
Right = right;
}
