Problem p01414 (C++) — buggy submission, verdict: Memory Limit Exceeded

#include <bits/stdc++.h>
using namespace std;

#define dump(n) cout << "# " << #n << '=' << (n) << endl
#define repi(i, a, b) for (int i = int(a); i < int(b); i++)
#define peri(i, a, b) for (int i = int(b); i-- > int(a);)
#define rep(i, n) repi(i, 0, n)
#define per(i, n) peri(i, 0, n)
#define all(c) begin(c), end(c)
#define mp make_pair
#define mt make_tuple

typedef unsigned int uint;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<string> vs;

const int INF = 1e9;
const int MOD = 1e9 + 7;
const double EPS = 1e-9;

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  return os << '(' << p.first << ',' << p.second << ')';
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &a) {
  os << '[';
  rep(i, a.size()) os << (i ? " " : "") << a[i];
  return os << ']';
}

int main() {
  for (int n; cin >> n && n;) {
    vi hs(n), ws(n);
    rep(i, n) cin >> hs[i] >> ws[i];
    vs grid(4);
    rep(i, 4) cin >> grid[i];

    queue<pii> q;
    q.emplace(0, 0);
    vi vis(1 << 16);
    while (q.size()) {
      int bit, turn;
      tie(bit, turn) = q.front();
      q.pop();
      if (bit == (1 << 16) - 1) {
        cout << turn << endl;
        break;
      }
      if (vis[bit])
        continue;
      vis[bit] = 1;

      rep(k, n) {
        repi(i0, -hs[k] + 1, 4) repi(j0, -ws[k] + 1, 4) {
          bool ok = true;
          char color = '?';
          int mask = 0;
          rep(i, hs[k]) rep(j, ws[k]) {
            if (i0 + i < 0 || 4 <= i0 + i || j0 + j < 0 || 4 <= j0 + j)
              continue;
            mask |= 1 << (i0 + i) * 4 + (j0 + j);
            if (bit >> (i0 + i) * 4 + (j0 + j) & 1)
              continue;
            if (color == '?')
              color = grid[i0 + i][j0 + j];
            if (grid[i0 + i][j0 + j] != color)
              ok = false;
          }
          if (ok && !vis[bit | mask])
            q.emplace(bit | mask, turn + 1);
        }
      }
    }
  }
}

Error: MLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;

#define dump(n) cout << "# " << #n << '=' << (n) << endl
#define repi(i, a, b) for (int i = int(a); i < int(b); i++)
#define peri(i, a, b) for (int i = int(b); i-- > int(a);)
#define rep(i, n) repi(i, 0, n)
#define per(i, n) peri(i, 0, n)
#define all(c) begin(c), end(c)
#define mp make_pair
#define mt make_tuple

typedef unsigned int uint;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<string> vs;

const int INF = 1e9;
const int MOD = 1e9 + 7;
const double EPS = 1e-9;

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  return os << '(' << p.first << ',' << p.second << ')';
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &a) {
  os << '[';
  rep(i, a.size()) os << (i ? " " : "") << a[i];
  return os << ']';
}

int main() {
  for (int n; cin >> n && n;) {
    vi hs(n), ws(n);
    rep(i, n) cin >> hs[i] >> ws[i];
    vs grid(4);
    rep(i, 4) cin >> grid[i];

    queue<pii> q;
    q.emplace(0, 0);
    vi vis(1 << 16);
    while (q.size()) {
      int bit, turn;
      tie(bit, turn) = q.front();
      q.pop();
      if (bit == (1 << 16) - 1) {
        cout << turn << endl;
        break;
      }
      if (vis[bit])
        continue;
      vis[bit] = 1;

      rep(k, n) {
        repi(i0, -hs[k] + 1, 4) repi(j0, -ws[k] + 1, 4) {
          bool ok = true;
          char color = '?';
          int mask = 0;
          rep(i, hs[k]) rep(j, ws[k]) {
            if (i0 + i < 0 || 4 <= i0 + i || j0 + j < 0 || 4 <= j0 + j)
              continue;
            mask |= 1 << (i0 + i) * 4 + (j0 + j);
            if (bit >> (i0 + i) * 4 + (j0 + j) & 1)
              continue;
            if (color == '?')
              color = grid[i0 + i][j0 + j];
            if (grid[i0 + i][j0 + j] != color)
              ok = false;
          }
          if (ok)
            q.emplace(bit | mask, turn + 1);
        }
      }
    }
  }
}