AOC 24 Day 6 Part 2 v2 C++ Solution

#include <fstream>
#include <iostream>
#include <string>
#include <vector>
#include <unordered_set>

const int steps[4][2] = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}};

struct vector_hash {
    std::size_t operator()(std::vector<int> const& vec) const {
        std::size_t seed = vec.size();
        for(auto x : vec) {
            x = ((x >> 16) ^ x) * 0x45d9f3b;
            x = ((x >> 16) ^ x) * 0x45d9f3b;
            x = (x >> 16) ^ x;
            seed ^= x + 0x9e3779b9 + (seed << 6) + (seed >> 2);
        }
        return seed;
    }
};

bool stop_check(int x, int y, int nrows, int ncols){
    if(x >= nrows || x < 0 || y < 0 || y >= ncols)
        return true;
    return false;
}

void change_pos(int& x, int& y, int cur_dir, char op){
    if(op == '+'){
        x += steps[cur_dir][0];
        y += steps[cur_dir][1];
    } else if(op == '-'){
        x -= steps[cur_dir][0];
        y -= steps[cur_dir][1];
    }
}

bool place_obstacle(std::vector<std::string>& guard_map, int x, int y, int cur_dir)
{
    std::unordered_set<std::vector<int>, vector_hash> visited_obs;
    int nrows = guard_map.size();
    int ncols = guard_map[0].size();
    bool quit = false;
    while(!quit){
        while(!(quit = stop_check(x, y, nrows, ncols)) && guard_map[x][y] != '#' ){
            change_pos(x, y, cur_dir, '+');
        }
        if(quit != true){
            std::vector<int> t{x, y, cur_dir};
            if(visited_obs.find(t) != visited_obs.end())
                return true;
            visited_obs.insert(t);
        }
        change_pos(x, y, cur_dir, '-');
        cur_dir = (cur_dir + 1) % 4;
    }
    return false;
}

int main()
{
    std::ifstream inp_file;
    std::vector<std::string> guard_map;
    int st_x, st_y;
    int cur_dir;
    inp_file.open("day6-in.txt");
    if(inp_file.is_open()){
        std::string line;
        bool f = false;
        while(std::getline(inp_file, line)){
            guard_map.push_back(line);
            for(int i = 0; !f && i < line.size(); i++){
                if(line[i] == '^'){
                    st_x = guard_map.size() - 1;
                    st_y = i;
                    f = true;
                }
            }
        }
    }
    inp_file.close();
    int nrows, ncols;
    bool quit = false;
    int pos_visited = 1;
    int nobstacle_pos = 0;

    nrows = guard_map.size();
    ncols = guard_map[0].size();
    int x,y;

    //part 1
    x = st_x;
    y = st_y;
    cur_dir = 0;
    while(!quit){
        while(guard_map[x][y] != '#'){
            if(guard_map[x][y] == '.'){
                pos_visited++;
                guard_map[x][y] = 'X';
            }
            change_pos(x, y, cur_dir, '+');
            if((quit = stop_check(x, y, nrows, ncols)))
                break;
        }
        change_pos(x, y, cur_dir, '-');
        cur_dir = (cur_dir + 1) % 4;
    }
    std::cout << pos_visited << std::endl;

    //part 2
    quit = false;
    x = st_x;
    y = st_y;
    cur_dir = 0;
    while(!quit){
        while(!(quit = stop_check(x, y, nrows, ncols)) &&  guard_map[x][y] != '#'){
            if(guard_map[x][y] == 'X'){
                guard_map[x][y] = '#';
                if(place_obstacle(guard_map, x - steps[cur_dir][0], y - steps[cur_dir][1], cur_dir)){
                    nobstacle_pos++;
                }
                guard_map[x][y] = '-';
            }
            change_pos(x, y, cur_dir, '+');

        }
        change_pos(x, y, cur_dir, '-');
        cur_dir = (cur_dir + 1) % 4;
    }
    std::cout << nobstacle_pos << std::endl;
    return 0;
}