public static void SolvePuzzle8_P2(string inputFile)
{
List <InstructionP2> instructionSet = new List <InstructionP2>();
using (StreamReader sr = new StreamReader(inputFile))
{
string buffer = sr.ReadLine();
while (buffer != null)
{
var instruct = buffer.Split(' ');
instructionSet.Add(new InstructionP2(instruct[0], instruct[1]));
buffer = sr.ReadLine();
}
}
long accumulator = 0;
int curIndex = 0;
HashSet <int> visitedIndexes = new HashSet <int>();
List <int> suspectIndicies = new List <int>();
while (true)
{
if (visitedIndexes.Contains(curIndex))
{
Console.WriteLine($"Reached operation to be executed a second time. Suspect list contains: {suspectIndicies.Count} items. ");
break;
}
visitedIndexes.Add(curIndex);
InstructionP2 CI = instructionSet[curIndex]; // just for readability.
switch (CI.Operation)
{
case "acc":
accumulator += CI.OpValue;
curIndex++;
break;
case "nop": // OpValue will always be 0
suspectIndicies.Add(curIndex);
curIndex++;
break;
case "jmp":
suspectIndicies.Add(curIndex);
curIndex += CI.OpValue;
break;
}
}
foreach (int sus in suspectIndicies)
{
accumulator = IterateWithSuspectIndex(instructionSet, sus);
if (accumulator != int.MinValue)
{
Console.WriteLine($"Completed iteration after changing index {sus}, accumulator = {accumulator}");
break;
}
}
}
private static long IterateWithSuspectIndex(List <InstructionP2> instructionSet, int suspectIndex)
{
long accumulator = 0;
int curIndex = 0;
HashSet <int> visitedIndexes = new HashSet <int>();
while (true)
{
if (visitedIndexes.Contains(curIndex))
{
Console.WriteLine($"Reached operation to be executed a second time. Suspect {suspectIndex} is not the culpruit.");
return(int.MinValue);
}
visitedIndexes.Add(curIndex);
InstructionP2 CI = instructionSet[curIndex]; // just for readability.
switch (CI.Operation)
{
case "acc":
accumulator += CI.OpValue;
curIndex++;
break;
case "nop": // OpValue will always be 0
if (curIndex == suspectIndex)
{
curIndex += CI.OpValue;
}
else
{
curIndex++;
}
break;
case "jmp":
if (curIndex == suspectIndex)
{
curIndex++;
}
else
{
curIndex += CI.OpValue;
}
break;
}
if (curIndex == instructionSet.Count)
{
return(accumulator);
}
}
}