private static ProgramTower ParseTower(string input)
{
var tower = new ProgramTower();
using (var sr = new StringReader(input))
{
while (true)
{
var line = sr.ReadLine();
if (line == null)
{
break;
}
var match = ProgramRegex.Match(line);
if (!match.Success)
{
throw new Exception("Regex failed; bad input");
}
var p = new Program(tower, match.Groups["name"].Value, int.Parse(match.Groups["weight"].Value));
var children = match.Groups["children"];
foreach (var child in match.Groups["children"].Captures)
{
p.AddChild(child.ToString());
}
tower.Add(p);
}
}
return(tower);
}
Program GetChildWithWrongWeight(ProgramTower tower, Program parent, out int expectedWeight)
{
expectedWeight = -1;
if (parent.Children == null)
{
return(null);
}
var children = parent.GetChildren();
children.Sort(CompareWeight);
if (children[0].TotalWeight() == children[1].TotalWeight())
{
expectedWeight = children[0].TotalWeight();
}
else if (children[children.Count - 1].TotalWeight() == children[children.Count - 2].TotalWeight())
{
expectedWeight = children[children.Count - 1].TotalWeight();
}
else
{
throw new Exception("what?");
}
Program childWrongWeight = null;
foreach (var child in children)
{
if (child.TotalWeight() != expectedWeight)
{
childWrongWeight = child;
break;
}
}
return(childWrongWeight);
}
string SolvePart1(string input)
{
/*
* Wandering further through the circuits of the computer, you come upon a tower
* of programs that have gotten themselves into a bit of trouble. A recursive
* algorithm has gotten out of hand, and now they're balanced precariously in a
* large tower.
*
* One program at the bottom supports the entire tower. It's holding a large
* disc, and on the disc are balanced several more sub-towers. At the bottom of
* these sub-towers, standing on the bottom disc, are other programs, each
* holding their own disc, and so on. At the very tops of these
* sub-sub-sub-...-towers, many programs stand simply keeping the disc below
* them balanced but with no disc of their own.
*
* You offer to help, but first you need to understand the structure of these
* towers. You ask each program to yell out their name, their weight, and (if
* they're holding a disc) the names of the programs immediately above them
* balancing on that disc. You write this information down (your puzzle input).
* Unfortunately, in their panic, they don't do this in an orderly fashion; by
* the time you're done, you're not sure which program gave which information.
*
* For example, if your list is the following:
*
* pbga (66)
* xhth (57)
* ebii (61)
* havc (66)
* ktlj (57)
* fwft (72) -> ktlj, cntj, xhth
* qoyq (66)
* padx (45) -> pbga, havc, qoyq
* tknk (41) -> ugml, padx, fwft
* jptl (61)
* ugml (68) -> gyxo, ebii, jptl
* gyxo (61)
* cntj (57)
* ...then you would be able to recreate the structure of the towers that looks like this:
*
* gyxo
* /
* ugml - ebii
* / \
| jptl
|
| pbga
| / /
| tknk --- padx - havc
\ \
| qoyq
|
| ktlj
\ /
\ fwft - cntj
\
\ xhth
\ In this example, tknk is at the bottom of the tower (the bottom program), and
\ is holding up ugml, padx, and fwft. Those programs are, in turn, holding up
\ other programs; in this example, none of those programs are holding up any
\ other programs, and are all the tops of their own towers. (The actual tower
\ balancing in front of you is much larger.)
\
\ Before you're ready to help them, you need to make sure your information is
\ correct. What is the name of the bottom program?
*/
ProgramTower tower = ParseTower(input);
var root = tower.Root;
return(root.Name);
}
public Program(ProgramTower tower, string name, int weight)
{
this.tower = tower;
Name = name;
Weight = weight;
}