Problem p03491 (C++)

Buggy submission (status: Runtime Error):
/* ---------- STL Libraries ---------- */

// IO library
#include <cstdio>
#include <fstream>
#include <iomanip>
#include <ios>
#include <iostream>

// algorithm library
#include <algorithm>
#include <cmath>
#include <numeric>

// container library
#include <array>
#include <bitset>
#include <deque>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>

/* ---------- Namespace ---------- */

using namespace std;

/* ---------- Type Abbreviation ---------- */

template <typename T> using V = vector<T>;
template <typename T, typename U> using P = pair<T, U>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using GPQ = priority_queue<T, vector<T>, greater<T>>;

using ll = long long;

#define fst first
#define snd second
#define pb push_back
#define mp make_pair
#define mt make_tuple

/* ---------- conversion ---------- */

#define INT(c) static_cast<int>(c)
#define CHAR(n) static_cast<char>(n)
#define LL(n) static_cast<ll>(n)
#define DOUBLE(n) static_cast<double>(n)

/* ---------- container ---------- */

#define ALL(v) (v).begin(), (v).end()
#define SIZE(v) (LL((v).size()))

#define FIND(v, k) (v).find(k) != (v).end()
#define VFIND(v, k) find(ALL(v), k) != (v).end()

#define gsort(b, e) sort(b, e, greater<decltype(*b)>())
#define SORT(v) sort(ALL(v))
#define GSORT(v) gsort(ALL(v))

/* ---------- repetition ---------- */

#define FOR(i, a, b) for (ll i = (a); i <= (b); ++i)
#define RFOR(i, a, b) for (ll i = (a); i >= (b); --i)

/* ----------- debug ---------- */

template <class T> ostream &operator<<(ostream &os, vector<T> v) {
  os << "[";
  for (auto vv : v)
    os << vv << ",";
  return os << "]";
}

template <class T> ostream &operator<<(ostream &os, set<T> v) {
  os << "[";
  for (auto vv : v)
    os << vv << ",";
  return os << "]";
}

template <class L, class R> ostream &operator<<(ostream &os, pair<L, R> p) {
  return os << "(" << p.fst << "," << p.snd << ")";
}

/* ---------- Constants ---------- */

// const ll MOD = 1e9 + 7;
// const int INF = 1 << 25;
// const ll INF = 1LL << 50;
// const double PI = acos(-1);
// const double EPS = 1e-10;
// const ll dx[4] = {0, -1, 1, 0};
// const ll dy[4] = {-1, 0, 0, 1};

/* ---------- Short Functions ---------- */

template <typename T> T sq(T a) { return a * a; }

template <typename T> T gcd(T a, T b) {
  if (a > b)
    return gcd(b, a);
  return a == 0 ? b : gcd(b % a, a);
}

template <typename T, typename U> T mypow(T b, U n) {
  if (n == 0)
    return 1;
  if (n == 1)
    return n /* % MOD */;
  if (n % 2 == 0) {
    return mypow(sq(b) /* % MOD */, n / 2);
  } else {
    return mypow(b, n - 1) * b /* % MOD */;
  }
}

ll pcnt(ll b) { return __builtin_popcountll(b); }

/* v-v-v-v-v-v-v-v-v Main Part v-v-v-v-v-v-v-v-v */

#define DEBUG
#define DEBUG_CASE_NUM 6

struct node {
  explicit node(ll _d) : d(_d) { child[0] = child[1] = -1; }

  ll d;
  ll child[2];
};

V<node> tree;
ll N, L;

ll grundy(ll n) {
  ll ret = 1;
  while (n % 2 == 0) {
    n /= 2;
    ret *= 2;
  }

  return ret;
}

ll dfs(ll v) {
  if (tree[v].child[0] < 0 && tree[v].child[1] < 0) {
    return 0;
  }

  ll ret = 0;

  FOR(i, 0, 1) {
    if (tree[v].child[i] < 0) {
      ret ^= grundy(L - tree[v].d);
    } else {
      ret ^= dfs(tree[v].child[i]);
    }
  }

  return ret;
}

void solve() {
  tree.clear();

  cin >> N >> L;

  tree.pb(node(0));

  FOR(_, 1, N) {
    string S;
    cin >> S;

    ll now = 0;
    for (char c : S) {
      if (tree[now].child[c - '0'] >= 0) {
        now = tree[now].child[c - '0'];
      } else {
        tree[now].child[c - '0'] = SIZE(tree);
        tree.pb(node(tree[now].d + 1));
        now = tree[now].child[c - '0'];
      }
    }
  }

  cout << (dfs(0) > 0 ? "Alice" : "Bob") << endl;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  // cout << fixed << setprecision(10);

#ifdef DEBUG
  freopen("input.txt", "r", stdin);
  FOR(_, 1, DEBUG_CASE_NUM) {
    solve();
    cout << "++++++++++" << endl;
  }
#else
  solve();
#endif

  return 0;
}


Fixed submission:
/* ---------- STL Libraries ---------- */

// IO library
#include <cstdio>
#include <fstream>
#include <iomanip>
#include <ios>
#include <iostream>

// algorithm library
#include <algorithm>
#include <cmath>
#include <numeric>

// container library
#include <array>
#include <bitset>
#include <deque>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>

/* ---------- Namespace ---------- */

using namespace std;

/* ---------- Type Abbreviation ---------- */

template <typename T> using V = vector<T>;
template <typename T, typename U> using P = pair<T, U>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using GPQ = priority_queue<T, vector<T>, greater<T>>;

using ll = long long;

#define fst first
#define snd second
#define pb push_back
#define mp make_pair
#define mt make_tuple

/* ---------- conversion ---------- */

#define INT(c) static_cast<int>(c)
#define CHAR(n) static_cast<char>(n)
#define LL(n) static_cast<ll>(n)
#define DOUBLE(n) static_cast<double>(n)

/* ---------- container ---------- */

#define ALL(v) (v).begin(), (v).end()
#define SIZE(v) (LL((v).size()))

#define FIND(v, k) (v).find(k) != (v).end()
#define VFIND(v, k) find(ALL(v), k) != (v).end()

#define gsort(b, e) sort(b, e, greater<decltype(*b)>())
#define SORT(v) sort(ALL(v))
#define GSORT(v) gsort(ALL(v))

/* ---------- repetition ---------- */

#define FOR(i, a, b) for (ll i = (a); i <= (b); ++i)
#define RFOR(i, a, b) for (ll i = (a); i >= (b); --i)

/* ----------- debug ---------- */

template <class T> ostream &operator<<(ostream &os, vector<T> v) {
  os << "[";
  for (auto vv : v)
    os << vv << ",";
  return os << "]";
}

template <class T> ostream &operator<<(ostream &os, set<T> v) {
  os << "[";
  for (auto vv : v)
    os << vv << ",";
  return os << "]";
}

template <class L, class R> ostream &operator<<(ostream &os, pair<L, R> p) {
  return os << "(" << p.fst << "," << p.snd << ")";
}

/* ---------- Constants ---------- */

// const ll MOD = 1e9 + 7;
// const int INF = 1 << 25;
// const ll INF = 1LL << 50;
// const double PI = acos(-1);
// const double EPS = 1e-10;
// const ll dx[4] = {0, -1, 1, 0};
// const ll dy[4] = {-1, 0, 0, 1};

/* ---------- Short Functions ---------- */

template <typename T> T sq(T a) { return a * a; }

template <typename T> T gcd(T a, T b) {
  if (a > b)
    return gcd(b, a);
  return a == 0 ? b : gcd(b % a, a);
}

template <typename T, typename U> T mypow(T b, U n) {
  if (n == 0)
    return 1;
  if (n == 1)
    return n /* % MOD */;
  if (n % 2 == 0) {
    return mypow(sq(b) /* % MOD */, n / 2);
  } else {
    return mypow(b, n - 1) * b /* % MOD */;
  }
}

ll pcnt(ll b) { return __builtin_popcountll(b); }

/* v-v-v-v-v-v-v-v-v Main Part v-v-v-v-v-v-v-v-v */

// #define DEBUG
// #define DEBUG_CASE_NUM 6

struct node {
  explicit node(ll _d) : d(_d) { child[0] = child[1] = -1; }

  ll d;
  ll child[2];
};

V<node> tree;
ll N, L;

ll grundy(ll n) {
  ll ret = 1;
  while (n % 2 == 0) {
    n /= 2;
    ret *= 2;
  }

  return ret;
}

ll dfs(ll v) {
  if (tree[v].child[0] < 0 && tree[v].child[1] < 0) {
    return 0;
  }

  ll ret = 0;

  FOR(i, 0, 1) {
    if (tree[v].child[i] < 0) {
      ret ^= grundy(L - tree[v].d);
    } else {
      ret ^= dfs(tree[v].child[i]);
    }
  }

  return ret;
}

void solve() {
  tree.clear();

  cin >> N >> L;

  tree.pb(node(0));

  FOR(_, 1, N) {
    string S;
    cin >> S;

    ll now = 0;
    for (char c : S) {
      if (tree[now].child[c - '0'] >= 0) {
        now = tree[now].child[c - '0'];
      } else {
        tree[now].child[c - '0'] = SIZE(tree);
        tree.pb(node(tree[now].d + 1));
        now = tree[now].child[c - '0'];
      }
    }
  }

  cout << (dfs(0) > 0 ? "Alice" : "Bob") << endl;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  // cout << fixed << setprecision(10);

#ifdef DEBUG
  freopen("input.txt", "r", stdin);
  FOR(_, 1, DEBUG_CASE_NUM) {
    solve();
    cout << "++++++++++" << endl;
  }
#else
  solve();
#endif

  return 0;
}