Решение задачи Путь спелеолога с Меньшиков

#include <iostream>
#include <cstdio>
#include <vector>
#include <string>
#include <queue>
#include <limits>
 
using namespace std;
 
const int EMPTY = 0;
const int USED = 1;
int n;
vector<vector<vector<int> > > mas;
struct point
{
    int x,y,z;
    point(){}
    point(int Z, int X, int Y)
    {
        z = Z; x = X; y = Y;
    }
};
point base;
void input()
{
    scanf("%d\n",&n);
    mas = vector<vector<vector<int> > >(n,vector<vector<int> >(n,vector<int>(n,0)));
    char c;
    for (int z = 0; z < n; z++)
    {
        for (int x = 0; x < n; x++)
        {
            for (int y = 0; y < n; y++)
            {
                c = getchar();
                if (c == 'S')
                    base = point(z,x,y);
                mas[z][x][y] = (c == '#' ? USED : EMPTY);
            }
            getchar(); // '\n'
        }
        getchar(); // '\n'
    }           
}
int moveX[6] = {0 ,0, 0,0,-1,1};
int moveY[6] = {0 ,0,-1,1, 0,0};
int moveZ[6] = {-1,1, 0,0, 0,0};
bool correct(int z, int x, int y)
{
    if (z<0 || x<0 || y <0)
        return false;
    if (z==n || x==n || y==n)
        return false;
    return true;
}
void BFS()
{
    int steps = -1;
    queue<point> q;
    int init = 2;
    mas[base.z][base.x][base.y] = init; // количество шагов
    q.push(base);
    while (!q.empty())
    {
        point cur = q.front(); q.pop();
        if (cur.z == 0)
        {
            steps = mas[cur.z][cur.x][cur.y];
            break;
        }
        for (int i=0;i<6;i++)
        {
            int x = cur.x + moveX[i];
            int y = cur.y + moveY[i];
            int z = cur.z + moveZ[i];
            if (correct(z,x,y) && mas[z][x][y] == EMPTY)
            {
                mas[z][x][y] = mas[cur.z][cur.x][cur.y] + 1;
                q.push(point(z,x,y));
            }
        }
    }
    cout<<steps - init;
}
int main()
{
    freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);
 
    input();
    BFS();
    return 0;
}