AoC21/d02.cc

#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

enum cmd {
    CMD_FORWARD,
    CMD_DOWN,
    CMD_UP,
};

struct commands {
    enum cmd cmd;
    int pos;
};

int main(int argc, char *argv[]) {
    if (argc <= 1) return 1;

    vector<struct commands> commands;
    {
        ifstream input(argv[1]);
        if (!input.is_open()) return 1;
        for (string line; getline(input, line);) {
            struct commands command;

            unsigned split = line.find(' ');
            string cmd = line.substr(0, split);
            line.erase(0, split + 1);
            if (cmd == "forward") {
                command.cmd = CMD_FORWARD;
            } else if (cmd == "down") {
                command.cmd = CMD_DOWN;
            } else if (cmd == "up") {
                command.cmd = CMD_UP;
            }
            command.pos = stoi(line);
            commands.push_back(command);
        }
    }

    int pos_h = 0;
    int pos_d = 0;
    for (struct commands command : commands) {
        switch (command.cmd) {
        case CMD_FORWARD:
            pos_h += command.pos;
            break;
        case CMD_DOWN:
            pos_d += command.pos;
            break;
        case CMD_UP:
            pos_d -= command.pos;
            break;
        }
    }

    cout << pos_h * pos_d << endl;

    int aim = 0;
    pos_h = 0;
    pos_d = 0;
    for (struct commands command : commands) {
        switch (command.cmd) {
        case CMD_FORWARD:
            pos_h += command.pos;
            pos_d += aim * command.pos;
            break;
        case CMD_DOWN:
            aim += command.pos;
            break;
        case CMD_UP:
            aim -= command.pos;
            break;
        }
    }

    cout << pos_h * pos_d << endl;
}