124 lines
3.0 KiB
C++
124 lines
3.0 KiB
C++
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#include <fstream>
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#include <iostream>
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#include <sstream>
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#include <vector>
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#include <unordered_map>
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enum Directions {
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UP,
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DOWN,
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LEFT,
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RIGHT
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};
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struct Command {
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Directions direction;
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int steps;
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};
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struct Position {
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int x;
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int y;
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};
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Directions charToDirection(char c) {
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switch(c) {
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case 'R':
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return RIGHT;
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case 'L':
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return LEFT;
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case 'U':
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return UP;
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case 'D':
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return DOWN;
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}
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std::cerr << "Invalid direction" << std::endl;
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exit(1);
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}
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std::vector<Command> getCommands( std::ifstream &file ) {
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std::vector<Command> ret{};
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int tmp_i = 0;
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char tmp_c = 0;
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std::string str;
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while ( std::getline( file, str ) ) {
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std::stringstream ss( str );
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ss >> tmp_c;
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ss >> tmp_i;
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ret.push_back({charToDirection(tmp_c), tmp_i});
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}
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return ret;
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}
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void handleMovement(const Position &head, Position &tail) {
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auto x_diff = head.x - tail.x;
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auto y_diff = head.y - tail.y;
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if(abs(x_diff) > 1 || abs(y_diff) > 1) {
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if(x_diff != 0) {
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x_diff /= abs(x_diff);
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}
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if(y_diff != 0) {
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y_diff /= abs(y_diff);
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}
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tail.x += x_diff;
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tail.y += y_diff;
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}
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}
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int ropeSimulation(const std::vector<Command> &commands, int rope_length) {
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std::vector<Position> positions;
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positions.resize(rope_length);
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for(int i = 0; i < rope_length; i++) {
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positions[i] = {0, 0};
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}
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std::unordered_map<int, std::unordered_map<int, bool>> visits{};
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visits[0][0] = true;
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for(auto &command : commands) {
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Position addition{0, 0};
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switch(command.direction) {
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case RIGHT:
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addition = {1, 0};
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break;
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case LEFT:
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addition = {-1, 0};
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break;
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case UP:
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addition = {0, -1};
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break;
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case DOWN:
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addition = {0, 1};
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break;
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}
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for(int i = 0; i < command.steps; i++) {
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positions[0].x += addition.x;
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positions[0].y += addition.y;
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for(int i = 1; i < rope_length; i++) {
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handleMovement(positions[i-1], positions[i]);
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}
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visits[positions.back().x][positions.back().y] = true;
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}
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}
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int result = 0;
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for(auto &visit : visits) {
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result += visit.second.size();
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}
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return result;
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}
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int part1(const std::vector<Command> &commands) {
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return ropeSimulation(commands, 2);
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}
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int part2(const std::vector<Command> &commands) {
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return ropeSimulation(commands, 10);
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}
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int main() {
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std::ifstream input_file( "input" );
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auto commands = getCommands( input_file );
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std::cout << "The rope's tail visits \033[91;1m" << part1(commands)
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<< "\033[0m positions." << std::endl;
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std::cout << "The long rope's tail visits \033[91;1m" << part2(commands)
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<< "\033[0m positions." << std::endl;
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}
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