Big beard AOC 2024 Day 6 Part 1

aoc-2024-6-1.cpp

#include <iostream>
#include <fstream>
#include <string>
#include <ctype.h>
#include <vector>
#include <algorithm>
#include <unordered_map>
#include <sstream>
#include <regex>
#include <utility>

using namespace std;

enum Dir {
    UP, RIGHT, DOWN, LEFT
};

struct Vec {
    Vec(int x, int y, Dir d) : x(x), y(y), d(d) {}
    int x;
    int y;
    Dir d;
};

void markGuardSteps(std::vector<std::string>& grid, int x, int y, int rows, int cols)
{
    Vec up(-1, 0, UP);
    Vec right(0, 1, RIGHT);
    Vec down(1, 0, DOWN);
    Vec left(0, -1, LEFT);
    Vec currentDir = up;
    int prevx = x;
    int prevy = y;
    while (x >= 0 && y >= 0 && x < rows && y < cols) {
        // While we are in the bounds of the grid, keep marking the steps.
        char currentTerrain = grid[x][y];

        if (currentTerrain != '#') {
            grid[x][y] = 'X';
        }
        else {
            // We have hit a crate
            // Get to the previous position and change the direction to the right.
            x = prevx;
            y = prevy;
            if (currentDir.d == UP) {
                currentDir = right;
            }
            else if (currentDir.d == RIGHT) {
                currentDir = down;
            }
            else if (currentDir.d == DOWN) {
                currentDir = left;
            }
            else {
                currentDir = up;
            }
        }
        // store the previous position
        prevx = x;
        prevy = y;
        // Apply the direction with speed 1 cell
        x += currentDir.x;
        y += currentDir.y;
    }
}

int countMarked(std::vector<std::string>& grid)
{
    int count = 0;

    for (auto& str : grid) {
        for (char c : str) {
            if (c == 'X') {
                count++;
            }
        }
    }

    return count;
}

int main()
{
    ifstream infile("input.txt");

    if (!infile.is_open()) {
        cout << "File prob\n";
        return -1;
    }
    string line;
    std::vector<std::string> grid;
    int guardx = 0, guardy = 0;
    int lineCount = 0;
    int colsCount = 0;
    while (infile.good()) {
        getline(infile, line);
        if (line.empty()) break;
        
        auto pos = line.find('^');
        if (pos != -1) {
            guardx = lineCount;
            guardy = pos;
            colsCount = line.size();
        }

        grid.push_back(line);
        lineCount++;
    }

    markGuardSteps(grid, guardx, guardy, grid.size(), colsCount);
    int a = countMarked(grid);
    std::cout << a << std::endl;
}