Language: C++

#include <bits/stdc++.h>
#define _GLIBCXX_DEBUG
using namespace std;
using ll = long long;
using vec = vector<ll>;
using vect = vector<double>;
using Graph = vector<vector<ll>>;
#define loop(i, n) for (ll i = 0; i < n; i++)
#define Loop(i, m, n) for (ll i = m; i < n; i++)
#define pool(i, n) for (ll i = n; i >= 0; i--)
#define Pool(i, m, n) for (ll i = n; i >= m; i--)
#define mod 1000000007ll
#define flagcount __builtin_popcount
#define flag(x) (1 << x)
#define flagadd(bit, x) bit |= flag(x)
#define flagpop(bit, x) bit &= ~flag(x)
#define flagon(bit, i) bit &flag(i)
#define flagoff(bit, i) !(bit & (1 << i))
#define all(v) v.begin(), v.end()
#define low2way(v, x) lower_bound(all(v), x)
#define high2way(v, x) upper_bound(all(v), x)
#define idx_lower(v, x) (distance(v.begin(), low2way(v, x)))  //配列vでx未満の要素数を返す
#define idx_upper(v, x) (distance(v.begin(), high2way(v, x))) //配列vでx以下の要素数を返す
#define idx_lower2(v, x) (v.size() - idx_lower(v, x))         //配列vでx以上の要素数を返す
#define idx_upper2(v, x) (v.size() - idx_upper(v, x))         //配列vでxより大きい要素の数を返す
#define putout(a) cout << a << endl
#define Gput(a, b) G[a].push_back(b)
#define Sum(v) accumulate(all(v), 0ll)
#define gcd(x, y) __gcd(x, y)
ll ctoi(char c)
{
    if (c >= '0' && c <= '9')
    {
        return c - '0';
    }
    return 0;
}
template <typename T>
T lcm(T x, T y)
{
    T z = gcd(x, y);
    return x * y / z;
}
template <typename T>
bool primejudge(T n)
{
    if (n < 2)
        return false;
    else if (n == 2)
        return true;
    else if (n % 2 == 0)
        return false;
    double sqrtn = sqrt(n);
    for (T i = 3; i < sqrtn + 1; i++)
    {
        if (n % i == 0)
        {
            return false;
        }
        i++;
    }
    return true;
}
//場合によって使い分ける
const ll dx[4] = {1, 0, -1, 0};
const ll dy[4] = {0, 1, 0, -1};
//const ll dx[8] = {1, 1, 0, -1, -1, -1, 0, 1};
//const ll dy[8] = {0, 1, 1, 1, 0, -1, -1, -1};
//2次元配列の宣言
//vector<vector<ll>> field(h, vector<ll>(w));
ll N;
vector<string> field;
ll bfs(ll sx, ll sy)
{
    
    dist[sx][sy] = 0;
    //0-1BFS(笑)
    deque<pair<ll, ll>> que;
    que.push_back({sx, sy});
    while (!que.empty())
    {
        pair<ll, ll> p = que.front();
        que.pop_front();
        ll x = p.first, y = p.second;
        loop(d, 4)
        {
            ll nx = x + dx[d], ny = y + dy[d];
            if (nx < 0 || nx >= N || ny < 0 || ny >= N)
            {
                return dist[x][y];
            }
            ll d2 = dist[x][y];
            if (field[nx][ny] == '#')
                d2++;
            if (dist[nx][ny] > d2)
            {
                dist[nx][ny] = d2;
                if (field[nx][ny] == '#')
                    que.push_back({nx, ny});
                else
                    que.push_front({nx, ny});
            }
        }
    }
}
int main()
{
    cout << fixed << setprecision(30);
    cin >> N;
    vec P(N * N);
    loop(i, N * N) cin >> P[i];
    string flat;
    loop(i, N) flat += '#';
    field.resize(N);
    loop(i, N) field[i] = flat;
    ll ans = 0;
    loop(i, N * N)
    {
        P[i]--;
        ll sx = P[i] % N;
        P[i] /= N;
        ll sy = P[i];
        field[sx][sy] = '.';
        if (sx == 0 || sx == N - 1 || sy == 0 || sy == N - 1)
            continue;
        ans += bfs(sx, sy);
    }
    putout(ans);
    return 0;
}


Compiler output:
a.cc: In function 'll bfs(ll, ll)':
a.cc:76:5: error: 'dist' was not declared in this scope
   76 |     dist[sx][sy] = 0;
      |     ^~~~