Problem p03491 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>

using namespace std;

#define int long long
// #define double long double
#define FOR(i, a, b) for (ll i = (a); i < (b); ++i)
#define FORR(i, a, b) for (ll i = (a); i > (b); --i)
#define REP(i, n) for (ll i = 0; i < (n); ++i)
#define REPR(i, n) for (ll i = n; i >= 0; i--)
#define FOREACH(x, a) for (auto &(x) : (a))
#define VECCIN(x)                                                              \
  for (auto &youso_ : (x))                                                     \
  cin >> youso_
#define bitcnt __builtin_popcount
#define SZ(x) ((ll)(x).size())
#define fi first
#define se second
#define All(a) (a).begin(), (a).end()
#define rAll(a) (a).rbegin(), (a).rend()

template <typename T = long long> inline T IN() {
  T x;
  cin >> x;
  return (x);
}
inline void CIN() {}
template <class Head, class... Tail>
inline void CIN(Head &&head, Tail &&...tail) {
  cin >> head;
  CIN(move(tail)...);
}
#define CCIN(...)                                                              \
  char __VA_ARGS__;                                                            \
  CIN(__VA_ARGS__)
#define DCIN(...)                                                              \
  double __VA_ARGS__;                                                          \
  CIN(__VA_ARGS__)
#define LCIN(...)                                                              \
  ll __VA_ARGS__;                                                              \
  CIN(__VA_ARGS__)
#define SCIN(...)                                                              \
  string __VA_ARGS__;                                                          \
  CIN(__VA_ARGS__)
#define Yes(a) cout << (a ? "Yes" : "No") << "\n"
#define YES(a) cout << (a ? "YES" : "NO") << "\n"
#define Printv(v)                                                              \
  {                                                                            \
    FOREACH(x, v) { cout << x << " "; }                                        \
    cout << "\n";                                                              \
  }
template <typename T = string> inline void eputs(T s) {
  cout << s << "\n";
  exit(0);
}
template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
  std::fill((T *)array, (T *)(array + N), val);
}

template <typename T> using PQG = priority_queue<T, vector<T>, greater<T>>;
template <typename T> using PQ = priority_queue<T>;

typedef long long ll;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<ll, ll> PL;
typedef vector<PL> VPL;
typedef vector<bool> VB;
typedef vector<double> VD;
typedef vector<string> VS;

const int INF = 1e9;
const int MOD = 1e9 + 7;
// const int MOD = 998244353;
const ll LINF = 5e18;
// const double PI = atan(1.0) * 4.0;
const ll dx[] = {1, 1, 0, -1, -1, -1, 0, 1};
const ll dy[] = {0, 1, 1, 1, 0, -1, -1, -1};
#define PI 3.141592653589793238

template <size_t X> struct Trie {
  struct Node {
    char c;
    array<int, X> nxt;
    vector<int> idxs;
    int idx;
    Node(char c) : c(c), idx(-1) { fill(nxt.begin(), nxt.end(), -1); }
  };

  using F = function<int(char)>;
  vector<Node> v;
  F conv;

  Trie(F conv, char c = '$') : conv(conv) { v.emplace_back(c); }

  void add(const string &s, int x) {
    int pos = 0;
    for (int i = 0; i < (int)s.size(); i++) {
      int k = conv(s[i]);
      if (~v[pos].nxt[k]) {
        pos = v[pos].nxt[k];
        continue;
      }
      int npos = v.size();
      v[pos].nxt[k] = npos;
      v.emplace_back(s[i]);
      pos = npos;
    }
    v[pos].idx = x;
    v[pos].idxs.emplace_back(x);
  }

  int find(const string &s) {
    int pos = 0;
    for (int i = 0; i < (int)s.size(); i++) {
      int k = conv(s[i]);
      if (v[pos].nxt[k] < 0)
        return -1;
      pos = v[pos].nxt[k];
    }
    return pos;
  }

  int find(int pos, char c) { return v[pos].nxt[conv(c)]; }

  int idx(int pos) { return pos < 0 ? -1 : v[pos].idx; }

  vector<int> idxs(int pos) { return pos < 0 ? vector<int>() : v[pos].idxs; }
};

auto f = [](char c) { return c - '0'; };
Trie<2> trie(f);
ll N, L;

ll grundy(ll height) {
  ll p = 1;
  while (height % p == 0)
    p << 1;
  return p;
}

ll dfs(ll pos, ll depth) {
  ll ret = 0;
  REP(b, 2) {
    ll npos = trie.find(pos, char('0' + b));
    if (npos < 0) {
      ret ^= grundy(L - depth);
      continue;
    }
    ll idx = trie.idx(npos);
    if (idx < 0)
      ret ^= dfs(npos, depth + 1LL);
  }
  return ret;
}

signed main() {
  cin >> N >> L;
  VS S(N);
  REP(i, N) {
    cin >> S[i];
    trie.add(S[i], i);
  }
  cout << (dfs(0, 0) ? "Alice" : "Bob") << "\n";
}

Fixed submission:
#include <bits/stdc++.h>

using namespace std;

#define int long long
// #define double long double
#define FOR(i, a, b) for (ll i = (a); i < (b); ++i)
#define FORR(i, a, b) for (ll i = (a); i > (b); --i)
#define REP(i, n) for (ll i = 0; i < (n); ++i)
#define REPR(i, n) for (ll i = n; i >= 0; i--)
#define FOREACH(x, a) for (auto &(x) : (a))
#define VECCIN(x)                                                              \
  for (auto &youso_ : (x))                                                     \
  cin >> youso_
#define bitcnt __builtin_popcount
#define SZ(x) ((ll)(x).size())
#define fi first
#define se second
#define All(a) (a).begin(), (a).end()
#define rAll(a) (a).rbegin(), (a).rend()

template <typename T = long long> inline T IN() {
  T x;
  cin >> x;
  return (x);
}
inline void CIN() {}
template <class Head, class... Tail>
inline void CIN(Head &&head, Tail &&...tail) {
  cin >> head;
  CIN(move(tail)...);
}
#define CCIN(...)                                                              \
  char __VA_ARGS__;                                                            \
  CIN(__VA_ARGS__)
#define DCIN(...)                                                              \
  double __VA_ARGS__;                                                          \
  CIN(__VA_ARGS__)
#define LCIN(...)                                                              \
  ll __VA_ARGS__;                                                              \
  CIN(__VA_ARGS__)
#define SCIN(...)                                                              \
  string __VA_ARGS__;                                                          \
  CIN(__VA_ARGS__)
#define Yes(a) cout << (a ? "Yes" : "No") << "\n"
#define YES(a) cout << (a ? "YES" : "NO") << "\n"
#define Printv(v)                                                              \
  {                                                                            \
    FOREACH(x, v) { cout << x << " "; }                                        \
    cout << "\n";                                                              \
  }
template <typename T = string> inline void eputs(T s) {
  cout << s << "\n";
  exit(0);
}
template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
  std::fill((T *)array, (T *)(array + N), val);
}

template <typename T> using PQG = priority_queue<T, vector<T>, greater<T>>;
template <typename T> using PQ = priority_queue<T>;

typedef long long ll;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<ll, ll> PL;
typedef vector<PL> VPL;
typedef vector<bool> VB;
typedef vector<double> VD;
typedef vector<string> VS;

const int INF = 1e9;
const int MOD = 1e9 + 7;
// const int MOD = 998244353;
const ll LINF = 5e18;
// const double PI = atan(1.0) * 4.0;
const ll dx[] = {1, 1, 0, -1, -1, -1, 0, 1};
const ll dy[] = {0, 1, 1, 1, 0, -1, -1, -1};
#define PI 3.141592653589793238

template <size_t X> struct Trie {
  struct Node {
    char c;
    array<int, X> nxt;
    vector<int> idxs;
    int idx;
    Node(char c) : c(c), idx(-1) { fill(nxt.begin(), nxt.end(), -1); }
  };

  using F = function<int(char)>;
  vector<Node> v;
  F conv;

  Trie(F conv, char c = '$') : conv(conv) { v.emplace_back(c); }

  void add(const string &s, int x) {
    int pos = 0;
    for (int i = 0; i < (int)s.size(); i++) {
      int k = conv(s[i]);
      if (~v[pos].nxt[k]) {
        pos = v[pos].nxt[k];
        continue;
      }
      int npos = v.size();
      v[pos].nxt[k] = npos;
      v.emplace_back(s[i]);
      pos = npos;
    }
    v[pos].idx = x;
    v[pos].idxs.emplace_back(x);
  }

  int find(const string &s) {
    int pos = 0;
    for (int i = 0; i < (int)s.size(); i++) {
      int k = conv(s[i]);
      if (v[pos].nxt[k] < 0)
        return -1;
      pos = v[pos].nxt[k];
    }
    return pos;
  }

  int find(int pos, char c) { return v[pos].nxt[conv(c)]; }

  int idx(int pos) { return pos < 0 ? -1 : v[pos].idx; }

  vector<int> idxs(int pos) { return pos < 0 ? vector<int>() : v[pos].idxs; }
};

auto f = [](char c) { return c - '0'; };
Trie<2> trie(f);
ll N, L;

ll grundy(ll height) {
  ll p = 1;
  while (height % p == 0)
    p <<= 1;
  return p;
}

ll dfs(ll pos, ll depth) {
  ll ret = 0;
  REP(b, 2) {
    ll npos = trie.find(pos, char('0' + b));
    if (npos < 0) {
      ret ^= grundy(L - depth);
      continue;
    }
    ll idx = trie.idx(npos);
    if (idx < 0)
      ret ^= dfs(npos, depth + 1LL);
  }
  return ret;
}

signed main() {
  cin >> N >> L;
  VS S(N);
  REP(i, N) {
    cin >> S[i];
    trie.add(S[i], i);
  }
  cout << (dfs(0, 0) ? "Alice" : "Bob") << "\n";
}