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advent-of-code-2020
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Add part 2 solution for day 12

master
Nick Krichevsky 2020-12-12 02:07:23 -05:00
parent 9e4d5e9287
commit f53e97ada8
1 changed files with 81 additions and 6 deletions
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87
day12/day12.cpp
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@ -9,15 +9,23 @@
constexpr int NUM_DIRECTIONS = 4;
enum CardinalDirection { NORTH = 0, EAST = 1, SOUTH = 2, WEST = 3 };
class Ship {
class MovablePoint {
public:
Ship(CardinalDirection direction, std::pair<int, int> position) : direction(direction), position(position) {
MovablePoint(CardinalDirection direction, std::pair<int, int> position) : direction(direction), position(position) {
}
const std::pair<int, int> &getPosition() const {
return this->position;
}
void setPosition(const std::pair<int, int> &position) {
this->position = position;
}
void setPosition(std::pair<int, int> &&position) {
this->position = position;
}
CardinalDirection getDirection() const {
return direction;
}
@ -31,7 +39,7 @@ class Ship {
}
void move(int value, CardinalDirection direction) {
int delta = (direction == SOUTH || direction == EAST) ? -value : value;
int delta = (direction == SOUTH || direction == WEST) ? -value : value;
if (direction == NORTH || direction == SOUTH) {
this->position.second += delta;
} else {
@ -48,6 +56,29 @@ class Ship {
this->addToDirection(deg / 90);
}
void rotatePosition(int degrees) {
int x = this->position.first;
int y = this->position.second;
// This is an awful way of writing a rotation, but it basically just hacking in the three parts of the rotation
// matrix I need
auto stepAmount = degrees / abs(degrees / 90);
if (abs(stepAmount) != 90) {
throw std::invalid_argument("Invalid rotation amount");
}
for (int i = 0; i < abs(degrees / 90); i++) {
int tmpX = x;
x = -y;
y = tmpX;
if (stepAmount < 0) {
x *= -1;
y *= -1;
}
}
this->position.first = x;
this->position.second = y;
}
private:
void addToDirection(int delta) {
this->direction = static_cast<CardinalDirection>((this->direction + delta) % NUM_DIRECTIONS);
@ -86,7 +117,7 @@ std::vector<std::pair<char, int>> parseInput(const std::vector<std::string> &inp
return parsedInput;
}
void makeMove(Ship &ship, const std::pair<char, int> &move) {
void moveShip(MovablePoint &ship, const std::pair<char, int> &move) {
char directive = move.first;
int magnitude = move.second;
switch (directive) {
@ -116,10 +147,53 @@ void makeMove(Ship &ship, const std::pair<char, int> &move) {
}
}
void moveShipOrWaypoint(MovablePoint &ship, MovablePoint &waypoint, const std::pair<char, int> &move) {
char directive = move.first;
int magnitude = move.second;
switch (directive) {
case 'L':
waypoint.rotatePosition(magnitude);
break;
case 'R':
waypoint.rotatePosition(-magnitude);
break;
case 'N':
waypoint.move(magnitude, NORTH);
break;
case 'S':
waypoint.move(magnitude, SOUTH);
break;
case 'E':
waypoint.move(magnitude, EAST);
break;
case 'W':
waypoint.move(magnitude, WEST);
break;
case 'F': {
auto shipPosition = ship.getPosition();
shipPosition.first += waypoint.getPosition().first * magnitude;
shipPosition.second += waypoint.getPosition().second * magnitude;
ship.setPosition(std::move(shipPosition));
} break;
default:
throw std::invalid_argument("Invalid move direction");
}
}
int part1(const std::vector<std::pair<char, int>> &input) {
Ship ship(EAST, std::pair<int, int>(0, 0));
MovablePoint ship(EAST, std::pair<int, int>(0, 0));
for (auto &move : input) {
makeMove(ship, move);
moveShip(ship, move);
}
return abs(ship.getPosition().first) + abs(ship.getPosition().second);
}
int part2(const std::vector<std::pair<char, int>> &input) {
MovablePoint ship(EAST, std::pair<int, int>(0, 0));
MovablePoint waypoint(EAST, std::pair<int, int>(10, 1));
for (auto &move : input) {
moveShipOrWaypoint(ship, waypoint, move);
}
return abs(ship.getPosition().first) + abs(ship.getPosition().second);
@ -135,4 +209,5 @@ int main(int argc, char *argv[]) {
auto parsedInput = parseInput(input);
std::cout << part1(parsedInput) << std::endl;
std::cout << part2(parsedInput) << std::endl;
}