//######################################################################
// Part 1 + 2 Solutions
//######################################################################
public static int Part1()
{
const string path = Helpers.inputPath + @"\day16\input.txt";
string input = ProcessInputFile(path);
IList <TicketValidator.Rule> rules = ParseRules(input);
TicketValidator validator = new TicketValidator();
validator.AddRules(rules);
IList <IList <int> > tickets = ParseNearbyTickets(input);
int errorRate = 0;
foreach (var ticket in tickets)
{
foreach (int val in ticket)
{
if (!validator.ValidateValue(val))
{
errorRate += val;
}
}
}
return(errorRate);
}
public static long Part2()
{
const string path = Helpers.inputPath + @"\day16\input.txt";
string input = ProcessInputFile(path);
IList <TicketValidator.Rule> rules = ParseRules(input);
TicketValidator validator = new TicketValidator();
validator.AddRules(rules);
IList <int> myTicket = ParseYourTicket(input);
IList <IList <int> > nearbyTickets = ParseNearbyTickets(input);
IList <string> fieldOrder = FindFieldOrder(validator, nearbyTickets);
long result = 1;
for (int i = 0; i < myTicket.Count; i++)
{
if (fieldOrder[i].StartsWith("departure"))
{
result *= (long)myTicket[i];
}
}
return(result);
}
public static IList <string> FindFieldOrder(TicketValidator validator, IList <IList <int> > tickets)
{
IList <IList <int> > validTickets = tickets.Where(t => validator.ValidateValues(t)).ToList();
int fieldCount = tickets[0].Count;
var fieldIndices = new Dictionary <string, ISet <int> >();
foreach (string field in validator.Rules)
{
var indices = new HashSet <int>(Enumerable.Range(0, fieldCount));
fieldIndices.Add(field, indices);
}
IList <string> result = new List <string>();
foreach (int i in Enumerable.Range(0, fieldCount))
{
result.Add("NONE");
}
// find which indices the field cannot be due to values breaking rules
foreach (var ticket in validTickets)
{
for (int i = 0; i < fieldCount; i++)
{
int val = ticket[i];
IList <string> invalidFields = validator.RulesBroken(val);
foreach (string field in invalidFields)
{
fieldIndices[field].Remove(i);
}
}
}
// deduce index assignments from remaining possible values
var assignedIndices = new HashSet <int>();
bool unassignedExists = false;
do
{
unassignedExists = false;
foreach (var field in fieldIndices)
{
// unassigned; ExceptWith removes any indices already assigned
if (field.Value.Count > 1)
{
unassignedExists = true;
field.Value.ExceptWith(assignedIndices);
}
// otherwise assign index
else
{
assignedIndices.Add(field.Value.First());
result[field.Value.First()] = field.Key;
}
}
} while (unassignedExists);
return(result);
}
