Problem p00606 (C++) — buggy submission, verdict: Memory Limit Exceeded

#include <bits/stdc++.h>

#define LL long long
#define VI vector<int>
#define VVI vector<vector<int>>
#define VVVI vector<vector<vector<int>>>
#define VL vector<LL>
#define VVL vector<vector<LL>>
#define VVVL vector<vector<vector<LL>>>
#define VB vector<bool>
#define FOR(i, a, b) for (int i = (a); i < ((int)b); ++i)
#define RFOR(i, a) for (int i = (a); i >= 0; --i)
#define FOE(i, a) for (auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define DUMP(x) cerr << #x << " = " << (x) << endl;
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v, x) (std::find(v.begin(), v.end(), x) != v.end())
#define BIT(n) (1LL << (n))
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());
#define EPS 1e-14

template <class T> T ceil(T a, T b) { return (a + b - 1) / b; }
template <class T> void print(T x) { std::cout << x << std::endl; }
bool inside(int y, int x, int H, int W) {
  return 0 <= y and y < H and 0 <= x and x < W;
}

const std::string YES = "YES", Yes = "Yes", NO = "NO", No = "No";
const std::vector<int> dy = {0, 1, 0, -1},
                       dx = {1, 0, -1, 0}; // 4近傍（右, 下, 左, 上）

using namespace std;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  while (true) {
    int N;
    cin >> N;
    if (N == 0) {
      break;
    }
    char S, T, B;
    cin >> S >> T >> B;
    int sy = (S - 'A') / 3;
    int sx = (S - 'A') % 3;
    int ty = (T - 'A') / 3;
    int tx = (T - 'A') % 3;
    int by = (B - 'A') / 3;
    int bx = (B - 'A') % 3;

    vector<vector<vector<double>>> dp(
        N + 1, vector<vector<double>>(3, vector<double>(3, 0)));
    dp[0][sy][sx] = 1;

    FOR(n, 0, N) {
      FOR(y, 0, 3) {
        FOR(x, 0, 3) {

          FOR(i, 0, 4) {
            int ny = y + dy[i];
            int nx = x + dx[i];

            if (inside(ny, nx, 3, 3) and not(ny == by and nx == bx)) {
              dp[n + 1][ny][nx] += dp[n][y][x] * 0.25;
            } else {
              dp[n + 1][y][x] += dp[n][y][x] * 0.25;
            }
          }
        }
      }
    }
    print(dp[N][ty][tx]);
  }
  return 0;
}


Error: MLE

Fixed submission:

#include <bits/stdc++.h>

#define LL long long
#define VI vector<int>
#define VVI vector<vector<int>>
#define VVVI vector<vector<vector<int>>>
#define VL vector<LL>
#define VVL vector<vector<LL>>
#define VVVL vector<vector<vector<LL>>>
#define VB vector<bool>
#define FOR(i, a, b) for (int i = (a); i < ((int)b); ++i)
#define RFOR(i, a) for (int i = (a); i >= 0; --i)
#define FOE(i, a) for (auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define DUMP(x) cerr << #x << " = " << (x) << endl;
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v, x) (std::find(v.begin(), v.end(), x) != v.end())
#define BIT(n) (1LL << (n))
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());
#define EPS 1e-14

template <class T> T ceil(T a, T b) { return (a + b - 1) / b; }
template <class T> void print(T x) { std::cout << x << std::endl; }
bool inside(int y, int x, int H, int W) {
  return 0 <= y and y < H and 0 <= x and x < W;
}

const std::string YES = "YES", Yes = "Yes", NO = "NO", No = "No";
const std::vector<int> dy = {0, 1, 0, -1},
                       dx = {1, 0, -1, 0}; // 4近傍（右, 下, 左, 上）

using namespace std;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  while (true) {
    int N;
    cin >> N;
    if (N == 0) {
      break;
    }
    char S, T, B;
    cin >> S >> T >> B;
    int sy = (S - 'A') / 3;
    int sx = (S - 'A') % 3;
    int ty = (T - 'A') / 3;
    int tx = (T - 'A') % 3;
    int by = (B - 'A') / 3;
    int bx = (B - 'A') % 3;

    vector<vector<vector<double>>> dp(
        N + 1, vector<vector<double>>(3, vector<double>(3, 0)));
    dp[N][sy][sx] = 1;

    queue<tuple<int, int, int>> que;
    que.push(make_tuple(N, sy, sx));

    while (not que.empty()) {
      int rest, y, x;
      tie(rest, y, x) = que.front();
      que.pop();
      if (rest == 0) {
        continue;
      }

      FOR(i, 0, 4) {
        int ny = y + dy[i];
        int nx = x + dx[i];

        if (inside(ny, nx, 3, 3) and not(ny == by and nx == bx)) {
          dp[rest - 1][ny][nx] += dp[rest][y][x] * 0.25;
          que.push(make_tuple(rest - 1, ny, nx));
        } else {
          dp[rest - 1][y][x] += dp[rest][y][x] * 0.25;
          que.push(make_tuple(rest - 1, y, x));
        }
      }
    }
    print(dp[0][ty][tx]);
  }
  return 0;
}