protected override int SolvePartOne()
{
AssemblyProgram program = new AssemblyProgram(lines);
InfiniteLoopDetector loopDetector = new InfiniteLoopDetector(program);
loopDetector.Execute();
return(program.Accumulator);
}
protected override int SolvePartTwo()
{
Queue <int> indicesWhichContainJmp = new Queue <int>();
Queue <int> indicesWhichContainNop = new Queue <int>();
// find all lines which contain a nop or jmp instruction
for (int i = 0; i < lines.Length; i++)
{
if (lines[i].StartsWith("nop"))
{
indicesWhichContainNop.Enqueue(i);
}
else if (lines[i].StartsWith("jmp"))
{
indicesWhichContainJmp.Enqueue(i);
}
}
InfiniteLoopDetector loopDetector;
AssemblyProgram program;
// iterate all lines which contain nop instruction
do
{
int index = indicesWhichContainNop.Dequeue();
lines[index] = lines[index].Replace("nop", "jmp");
program = new AssemblyProgram(lines);
loopDetector = new InfiniteLoopDetector(program);
// restore original program
lines[index] = lines[index].Replace("jmp", "nop");
} while (loopDetector.Execute() && indicesWhichContainNop.Count > 0);
int answer;
if (indicesWhichContainNop.Count > 0)
{
answer = program.Accumulator;
}
else
{
do
{
int index = indicesWhichContainJmp.Dequeue();
lines[index] = lines[index].Replace("jmp", "nop");
program = new AssemblyProgram(lines);
loopDetector = new InfiniteLoopDetector(program);
// restore original program
lines[index] = lines[index].Replace("nop", "jmp");
} while (loopDetector.Execute() && indicesWhichContainJmp.Count > 0);
answer = program.Accumulator;
}
return(answer);
}
public void LoopDetection_RetrunsCorrect()
{
var banks = new List <int>
{
0,
2,
7,
0
};
var numRedistributions = InfiniteLoopDetector.RedistributionsUntilLoopDetection(banks, out int loopCycles);
Assert.Equal(5, numRedistributions);
Assert.Equal(4, loopCycles);
}
