D-Wizzard in Maze, 0-1 bfs

#include <bits/stdc++.h>
// #include <atcoder/all>
using namespace std;
#define int long long
#define all(x) (x).begin(), (x).end()
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<pair<int, int>> vpi;
typedef pair<int, int> pi;
#define f first
#define s second
#define pb push_back
#define endl "\n"
#define yes cout << "YES" << endl
#define no cout << "NO" << endl
int dx[] = {-1, 0, 1, 0};
int dy[] = {0, 1, 0, -1};
const int mod1 = 1e9 + 7, mod2 = 998244353, INF = 2e18, N = 1005, L = 19;
int gcd(int a, int b) { return b == 0 ? a : gcd(b, a % b); }
// -----------------------------------------------------------------------------
int cost[N][N];
void solve()
{
    int n, m;
    cin >> n >> m;
    int sx, sy, ex, ey;
    cin >> sx >> sy >> ex >> ey;
    sx--, sy--, ex--, ey--;
    string grid[N];
    for (int i = 0; i < n; i++)
    {
        cin >> grid[i];
    }
    for (int i = 0; i < n; i++)
    {
        fill(cost[i], cost[i] + m, INF);
    }
    function<bool(int, int)> inside = [&](int x, int y)
    {
        return (x >= 0 && x < n && y >= 0 && y < m && grid[x][y] == '.');
    };
    deque<pi> dq;
    dq.push_back({sx, sy});
    cost[sx][sy] = 0;
    while (!dq.empty())
    {
        auto [x, y] = dq.front();
        dq.pop_front();
        // explore all directions first via A
        for (int i = 0; i < 4; i++)
        {
            int nx = x + dx[i];
            int ny = y + dy[i];
            if (inside(nx, ny) && cost[nx][ny] > cost[x][y])
            {
                cost[nx][ny] = cost[x][y];
                dq.push_front({nx, ny});
            }
        }
        // now via magic of B
        for (int dx = -2; dx <= 2; dx++)
        {
            for (int dy = -2; dy <= 2; dy++)
            {
                int nx = x + dx;
                int ny = y + dy;
                if (inside(nx, ny) && cost[nx][ny] > cost[x][y] + 1)
                {
                    cost[nx][ny] = cost[x][y] + 1;
                    dq.push_back({nx, ny});
                }
            }
        }
    }
    int ans = cost[ex][ey];
    cout << ((ans == (INF)) ? -1 : ans) << endl;
    return;
}

signed main()
{
    // __START__;
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int t = 1;
    // cin >> t;
    while (t--)
    {
        solve();
    }
    // __END__;
    return 0;
}