89 lines
2.4 KiB
D
89 lines
2.4 KiB
D
import std;
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void main()
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{
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slurp!(char, ulong)("input", "%c%d").getManhattanDistanceForInstructions.writeln;
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}
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enum Direction
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{
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east = 0,
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north = 1,
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west = 2,
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south = 3
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}
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alias Instruction = Tuple!(char, ulong);
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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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immutable Direction direction = Direction.east;
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private auto calculateXMovement(Direction direction, ulong value)
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{
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switch (direction) with (Direction)
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{
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case east:
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return value;
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case west:
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return -value;
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default:
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return 0;
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}
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}
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private auto calculateYMovement(Direction direction, ulong value)
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{
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switch (direction) with (Direction)
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{
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case north:
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return value;
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case south:
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return -value;
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default:
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return 0;
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}
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}
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ShipState withInstructionApplied(Instruction instruction)
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{
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return [
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'E': (ulong value) => ShipState(posX + value, posY, direction),
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'N': (ulong value) => ShipState(posX, posY + value, direction),
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'W': (ulong value) => ShipState(posX - value, posY, direction),
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'S': (ulong value) => ShipState(posX, posY - value, direction),
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'L': (ulong value) => ShipState(posX, posY,
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((direction + value / 90) % 4).to!Direction),
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'R': (ulong value) => ShipState(posX, posY,
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((direction - value / 90 + 4) % 4).to!Direction),
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'F': (ulong value) => ShipState(posX + calculateXMovement(direction,
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value), posY + calculateYMovement(direction, value), direction)
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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', 10UL), tuple('N', 3UL), tuple('F', 7UL), tuple('R', 90UL),
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tuple('F', 11UL)
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];
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assert(input.getManhattanDistanceForInstructions == 25);
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}
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