72 lines
2.2 KiB
D
72 lines
2.2 KiB
D
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import std;
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void main()
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{
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slurp!(char, long)("input", "%c%d").getManhattanDistanceForInstructions.writeln;
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}
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alias Instruction = Tuple!(char, long);
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alias RelativeWaypoint = Tuple!(long, long);
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auto rotateLeft(RelativeWaypoint relativeWaypoint, long n)
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{
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n = (n + 4) % 4;
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if (n == 0)
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return relativeWaypoint;
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return tuple(-relativeWaypoint[1], relativeWaypoint[0]).rotateLeft(n - 1);
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}
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struct ShipState
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{
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immutable long posX = 0;
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immutable long posY = 0;
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RelativeWaypoint relativeWaypoint = tuple(10, 1);
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ShipState withInstructionApplied(Instruction instruction)
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{
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return [
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'E': (long value) => ShipState(posX, posY,
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tuple(relativeWaypoint[0] + value, relativeWaypoint[1])),
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'N': (long value) => ShipState(posX, posY,
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tuple(relativeWaypoint[0], relativeWaypoint[1] + value)),
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'W': (long value) => ShipState(posX, posY,
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tuple(relativeWaypoint[0] - value, relativeWaypoint[1])),
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'S': (long value) => ShipState(posX, posY,
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tuple(relativeWaypoint[0], relativeWaypoint[1] - value)),
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'L': (long value) => ShipState(posX, posY,
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relativeWaypoint.rotateLeft(value / 90)),
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'R': (long value) => ShipState(posX, posY,
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relativeWaypoint.rotateLeft((360 - value) / 90)),
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'F': (long value) => ShipState(posX + relativeWaypoint[0] * value,
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posY + relativeWaypoint[1] * value, relativeWaypoint)
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][instruction[0]](instruction[1]);
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}
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ShipState withInstructionsApplied(Instruction[] instructions)
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{
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if (instructions.empty)
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{
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return this;
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}
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return withInstructionApplied(instructions[0]).withInstructionsApplied(instructions[1 .. $]);
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}
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}
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auto getManhattanDistanceForInstructions(Instruction[] instructions)
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{
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auto finalState = ShipState().withInstructionsApplied(instructions);
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return abs(finalState.posX) + abs(finalState.posY);
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}
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unittest
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{
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auto input = [
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tuple('F', 10L), tuple('N', 3L), tuple('F', 7L), tuple('R', 90L),
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tuple('F', 11L)
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];
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assert(input.getManhattanDistanceForInstructions == 286);
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}
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