part2.cpp

#include "Day17.hpp"

#include <queue>

#include "../util/Md5Provider.hpp"

using namespace std;

Result Day17::solve_p2(){
    Field maze[MAZE_SIZE][MAZE_SIZE] = {
        {   {false, WALL, DOOR, DOOR, WALL},
            {false, WALL, DOOR, DOOR, DOOR},
            {false, WALL, DOOR, DOOR, DOOR},
            {false, WALL, WALL, DOOR, DOOR} },

        {   {false, DOOR, DOOR, DOOR, WALL},
            {false, DOOR, DOOR, DOOR, DOOR},
            {false, DOOR, DOOR, DOOR, DOOR},
            {false, DOOR, WALL, DOOR, DOOR} },

        {   {false, DOOR, DOOR, DOOR, WALL},
            {false, DOOR, DOOR, DOOR, DOOR},
            {false, DOOR, DOOR, DOOR, DOOR},
            {false, DOOR, WALL, DOOR, DOOR} },

        {   {false, DOOR, DOOR, WALL, WALL},
            {false, DOOR, DOOR, WALL, DOOR},
            {false, DOOR, DOOR, WALL, DOOR},
            {true, DOOR, DOOR, DOOR, DOOR} },
    };

    queue<Task> tasks;
    tasks.push({0, 0, ""});

    Md5Provider md5;
    unsigned longest = 0;

    while( !tasks.empty() ){
        Task task = tasks.front();
        tasks.pop();

        Field *cell = &(maze[task.x][task.y]);

        if( cell->is_goal ){
            if( task.path.length() > longest ){
                longest = task.path.length();
            }
            continue;
        }

        string digest = md5.compute(data + task.path);
        // up
        if( cell->up == DOOR && is_open(digest[0]) ){
            tasks.push({task.x - 1, task.y, task.path + "U"});
        }

        // down
        if( cell->down == DOOR && is_open(digest[1]) ){
            tasks.push({task.x + 1, task.y, task.path + "D"});
        }

        // left
        if( cell->left == DOOR && is_open(digest[2]) ){
            tasks.push({task.x, task.y - 1, task.path + "L"});
        }

        // right
        if( cell->right == DOOR && is_open(digest[3]) ){
            tasks.push({task.x, task.y + 1, task.path + "R"});
        }
    }

    return {true, to_string(longest)};
}