Problem p02626 (C++) — buggy submission, verdict: Time Limit Exceeded

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

using ll = long long;
#define int ll

// [a -> b-1]
#define reps(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
// [0 -> a-1]
#define rep(i, a) reps(i, 0, (a))
// [a-1 -> b]
#define rreps(i, a, b) for (int i = (int)((a)-1); i >= (int)(b); i--)
// [a-1 -> 0]
#define rrep(i, a) rreps(i, a, 0)
#define all(v) (v).begin(), (v).end()
// next_permutation(all(v))
#define PERM(v) next_permutation(all(v))
/*sort(all(v));
 * (v).erase(unique(all(v)), v.end())*/
#define UNIQUE(v)                                                              \\
  sort(all(v));                                                                \\
  (v).erase(unique(all(v)), v.end())
// b is [a, c)
#define RANGE(a, b, c) ((a) <= (b) && (b) < (c))
// c is [a, e) && d is [b, f)
#define RANGE2D(a, b, c, d, e, f) (RANGE((a), (c), (e)) && RANGE((b), (d), (f)))
#define chmin(a, b) a = min(a, (b))
#define chmax(a, b) a = max(a, (b))
#define fcout cout << fixed << setprecision(15)
#define YES(f) cout << ((f) ? YES_STR : NO_STR) << endl;

#ifdef LOCAL_DEBUG_OPTION
namespace debug_print_n {
struct DebugPrint {
  template <class T, class U = remove_const_t<remove_reference_t<T>>>
  static enable_if_t<is_integral<U>::value && !is_same<U, bool>::value &&
                     !is_same<U, char>::value>
  DUMP_SUB_FUNCTION(T x) {
    cerr << x;
  }
  template <class T, class U = remove_const_t<remove_reference_t<T>>>
  static enable_if_t<is_same<U, bool>::value> DUMP_SUB_FUNCTION(T x) {
    if (x)
      cerr << "True";
    else
      cerr << "False";
  }
  template <class T, class U = remove_const_t<remove_reference_t<T>>>
  static enable_if_t<is_same<U, char>::value> DUMP_SUB_FUNCTION(T x) {
    cerr << '\\'' << x << '\\'';
  }
  template <class T, class U = remove_const_t<remove_reference_t<T>>>
  static enable_if_t<is_same<U, string>::value> DUMP_SUB_FUNCTION(T x) {
    cerr << '\\"' << x << '\\"';
  }
  template <class T>
  static enable_if_t<is_same<T, const char *>::value> DUMP_SUB_FUNCTION(T x) {
    cerr << string(x);
  }
  template <class T> static enable_if_t<true> DUMP_SUB_FUNCTION(vector<T> x) {
    cerr << '{';
    for (size_t i = 0; i < x.size(); i++) {
      if (i)
        cerr << ", ";
      DUMP_SUB_FUNCTION(x[i]);
    }
    cerr << '}';
  }
  template <class T, size_t N>
  static enable_if_t<true> DUMP_SUB_FUNCTION(array<T, N> x) {
    cerr << '{';
    for (size_t i = 0; i < x.size(); i++) {
      if (i)
        cerr << ", ";
      DUMP_SUB_FUNCTION(x[i]);
    }
    cerr << '}';
  }
  template <class T> static enable_if_t<true> DUMP_SUB_FUNCTION(set<T> x) {
    cerr << '[';
    size_t i = 0;
    for (auto itr = x.begin(); itr != x.end(); itr++, i++) {
      if (i)
        cerr << ", ";
      DUMP_SUB_FUNCTION(*itr);
    }
    cerr << ']';
  }
  template <class T, class U>
  static enable_if_t<true> DUMP_SUB_FUNCTION(map<T, U> x) {
    cerr << '[';
    size_t i = 0;
    for (auto itr = x.begin(); itr != x.end(); itr++, i++) {
      if (i)
        cerr << ", ";
      DUMP_SUB_FUNCTION(itr->first);
      cerr << " : ";
      DUMP_SUB_FUNCTION(itr->second);
    }
    cerr << ']';
  }
  template <class T, class U = remove_const_t<remove_reference_t<T>>>
  static enable_if_t<is_floating_point<U>::value> DUMP_SUB_FUNCTION(T x) {
    cerr << fixed << setprecision(5) << x;
  }
  template <class T, class U>
  static enable_if_t<true> DUMP_SUB_FUNCTION(pair<T, U> p) {
    cerr << '(';
    DUMP_SUB_FUNCTION(p.first);
    cerr << ", ";
    DUMP_SUB_FUNCTION(p.second);
    cerr << ')';
  }
  template <int num = 0, class... Args>
  static enable_if_t<num == sizeof...(Args)>
  DUMP_SUB_FUNCTION(tuple<Args...> t) {
    if (num)
      cerr << ')';
  }
  template <int num = 0, class... Args>
      static enable_if_t <
      num<sizeof...(Args)> DUMP_SUB_FUNCTION(tuple<Args...> t) {
    if (num == 0)
      cerr << '(';
    DUMP_SUB_FUNCTION(get<num>(t));
    if (num + 1 < sizeof...(Args))
      cerr << ", ";
    DUMP_SUB_FUNCTION<num + 1>(t);
  }
  template <long unsigned N>
  static enable_if_t<true> DUMP_SUB_FUNCTION(bitset<N> x) {
    cerr << x;
  }
};
void dump() { cerr << endl; }
template <class Head, class... Tail> void dump(Head &&head, Tail &&...tail) {
  DebugPrint::DUMP_SUB_FUNCTION(head);
  if (sizeof...(Tail) != 0) {
    cerr << ' ';
  }
  dump(forward<Tail>(tail)...);
}
} // namespace debug_print_n
using debug_print_n::dump;
#else
template <class... Args> void dump(Args &&...args) {}
#endif

namespace bit {
using u32 = uint_fast32_t;
using u64 = unsigned long long;
template <class T> constexpr T set(T bin, u32 pos) {
  return bin | (1ull << pos);
}
template <class T> constexpr T unset(T bin, u32 pos) {
  return bin & ~(1ull << pos);
}
template <class T> constexpr T get(T bin, u32 pos) {
  return bin & (1ull << pos);
}
template <class T> constexpr T mask(T bin, u32 digit) {
  return bin & ((1ull << digit) - 1);
}
template <class T> constexpr bool check(T bin, u32 pos) {
  return get(bin, pos);
}
constexpr u32 popcount(u64 bin) { return __builtin_popcountll(bin); }
} // namespace bit

signed main() {
  int N;
  cin >> N;
  int a, b;
  cin >> a >> b;
  int c = 0;
  rep(i, N - 2) {
    int t;
    cin >> t;
    c ^= t;
  }
  constexpr int inf = 1e18;
  vector<int[2][2]> dp(50);
  rep(i, 50) rep(j, 2) rep(k, 2) dp[i][j][k] = inf;
  dp[0][0][0] = 0;
  rep(i, 49) {
    rep(j, 2) {
      rep(k, 2) {
        int val = dp[i][j][k];
        if (val == inf)
          continue;
        auto update = [&](int x) {
          if (a <= x)
            return;
          if (bit::mask((a - x) ^ (b + x) ^ c, i + 1))
            return;
          int J = 0;
          int K = 0;
          if (j) {
            if (!bit::check(a, i))
              J = 1;
          }
          if (k) {
            if (bit::check(b, i))
              K = 1;
          }
          J = J || (bit::mask(a, i + 1) < x);
          K = K || ((bit::mask(b, i + 1) + x) >> i + 1);
          chmin(dp[i + 1][J][K], x);
        };
        update(val);
        update(bit::set(val, i));
      }
    }
  }
  int res = inf;
  rep(j, 2) rep(k, 2) { chmin(res, dp[49][j][k]); }
  if (res == inf)
    res = -1;
  cout << res << endl;
  return 0;
}


Error: TLE

Fixed submission:

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

using ll = long long;
#define int ll

// [a -> b-1]
#define reps(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
// [0 -> a-1]
#define rep(i, a) reps(i, 0, (a))
// [a-1 -> b]
#define rreps(i, a, b) for (int i = (int)((a)-1); i >= (int)(b); i--)
// [a-1 -> 0]
#define rrep(i, a) rreps(i, a, 0)
#define all(v) (v).begin(), (v).end()
// next_permutation(all(v))
#define PERM(v) next_permutation(all(v))
/*sort(all(v));
 * (v).erase(unique(all(v)), v.end())*/
#define UNIQUE(v)                                                              \\
  sort(all(v));                                                                \\
  (v).erase(unique(all(v)), v.end())
// b is [a, c)
#define RANGE(a, b, c) ((a) <= (b) && (b) < (c))
// c is [a, e) && d is [b, f)
#define RANGE2D(a, b, c, d, e, f) (RANGE((a), (c), (e)) && RANGE((b), (d), (f)))
#define chmin(a, b) a = min(a, (b))
#define chmax(a, b) a = max(a, (b))
#define fcout cout << fixed << setprecision(15)
#define YES(f) cout << ((f) ? YES_STR : NO_STR) << endl;

#ifdef LOCAL_DEBUG_OPTION
namespace debug_print_n {
struct DebugPrint {
  template <class T, class U = remove_const_t<remove_reference_t<T>>>
  static enable_if_t<is_integral<U>::value && !is_same<U, bool>::value &&
                     !is_same<U, char>::value>
  DUMP_SUB_FUNCTION(T x) {
    cerr << x;
  }
  template <class T, class U = remove_const_t<remove_reference_t<T>>>
  static enable_if_t<is_same<U, bool>::value> DUMP_SUB_FUNCTION(T x) {
    if (x)
      cerr << "True";
    else
      cerr << "False";
  }
  template <class T, class U = remove_const_t<remove_reference_t<T>>>
  static enable_if_t<is_same<U, char>::value> DUMP_SUB_FUNCTION(T x) {
    cerr << '\\'' << x << '\\'';
  }
  template <class T, class U = remove_const_t<remove_reference_t<T>>>
  static enable_if_t<is_same<U, string>::value> DUMP_SUB_FUNCTION(T x) {
    cerr << '\\"' << x << '\\"';
  }
  template <class T>
  static enable_if_t<is_same<T, const char *>::value> DUMP_SUB_FUNCTION(T x) {
    cerr << string(x);
  }
  template <class T> static enable_if_t<true> DUMP_SUB_FUNCTION(vector<T> x) {
    cerr << '{';
    for (size_t i = 0; i < x.size(); i++) {
      if (i)
        cerr << ", ";
      DUMP_SUB_FUNCTION(x[i]);
    }
    cerr << '}';
  }
  template <class T, size_t N>
  static enable_if_t<true> DUMP_SUB_FUNCTION(array<T, N> x) {
    cerr << '{';
    for (size_t i = 0; i < x.size(); i++) {
      if (i)
        cerr << ", ";
      DUMP_SUB_FUNCTION(x[i]);
    }
    cerr << '}';
  }
  template <class T> static enable_if_t<true> DUMP_SUB_FUNCTION(set<T> x) {
    cerr << '[';
    size_t i = 0;
    for (auto itr = x.begin(); itr != x.end(); itr++, i++) {
      if (i)
        cerr << ", ";
      DUMP_SUB_FUNCTION(*itr);
    }
    cerr << ']';
  }
  template <class T, class U>
  static enable_if_t<true> DUMP_SUB_FUNCTION(map<T, U> x) {
    cerr << '[';
    size_t i = 0;
    for (auto itr = x.begin(); itr != x.end(); itr++, i++) {
      if (i)
        cerr << ", ";
      DUMP_SUB_FUNCTION(itr->first);
      cerr << " : ";
      DUMP_SUB_FUNCTION(itr->second);
    }
    cerr << ']';
  }
  template <class T, class U = remove_const_t<remove_reference_t<T>>>
  static enable_if_t<is_floating_point<U>::value> DUMP_SUB_FUNCTION(T x) {
    cerr << fixed << setprecision(5) << x;
  }
  template <class T, class U>
  static enable_if_t<true> DUMP_SUB_FUNCTION(pair<T, U> p) {
    cerr << '(';
    DUMP_SUB_FUNCTION(p.first);
    cerr << ", ";
    DUMP_SUB_FUNCTION(p.second);
    cerr << ')';
  }
  template <int num = 0, class... Args>
  static enable_if_t<num == sizeof...(Args)>
  DUMP_SUB_FUNCTION(tuple<Args...> t) {
    if (num)
      cerr << ')';
  }
  template <int num = 0, class... Args>
      static enable_if_t <
      num<sizeof...(Args)> DUMP_SUB_FUNCTION(tuple<Args...> t) {
    if (num == 0)
      cerr << '(';
    DUMP_SUB_FUNCTION(get<num>(t));
    if (num + 1 < sizeof...(Args))
      cerr << ", ";
    DUMP_SUB_FUNCTION<num + 1>(t);
  }
  template <long unsigned N>
  static enable_if_t<true> DUMP_SUB_FUNCTION(bitset<N> x) {
    cerr << x;
  }
};
void dump() { cerr << endl; }
template <class Head, class... Tail> void dump(Head &&head, Tail &&...tail) {
  DebugPrint::DUMP_SUB_FUNCTION(head);
  if (sizeof...(Tail) != 0) {
    cerr << ' ';
  }
  dump(forward<Tail>(tail)...);
}
} // namespace debug_print_n
using debug_print_n::dump;
#else
template <class... Args> void dump(Args &&...args) {}
#endif

namespace bit {
using u32 = uint_fast32_t;
using u64 = unsigned long long;
template <class T> constexpr T set(T bin, u32 pos) {
  return bin | (1ull << pos);
}
template <class T> constexpr T unset(T bin, u32 pos) {
  return bin & ~(1ull << pos);
}
template <class T> constexpr T get(T bin, u32 pos) {
  return bin & (1ull << pos);
}
template <class T> constexpr T mask(T bin, u32 digit) {
  return bin & ((1ull << digit) - 1);
}
template <class T> constexpr bool check(T bin, u32 pos) {
  return get(bin, pos);
}
constexpr u32 popcount(u64 bin) { return __builtin_popcountll(bin); }
} // namespace bit

signed main() {
  int N;
  cin >> N;
  int a, b;
  cin >> a >> b;
  int c = 0;
  rep(i, N - 2) {
    int t;
    cin >> t;
    c ^= t;
  }
  rep(i, a) {
    if (((a - i) ^ (b + i)) == c) {
      cout << i << endl;
      return 0;
    }
  }
  constexpr int inf = 1e18;
  vector<int[2][2]> dp(50);
  rep(i, 50) rep(j, 2) rep(k, 2) dp[i][j][k] = inf;
  dp[0][0][0] = 0;
  rep(i, 49) {
    rep(j, 2) {
      rep(k, 2) {
        int val = dp[i][j][k];
        if (val == inf)
          continue;
        auto update = [&](int x) {
          if (a <= x)
            return;
          if (bit::mask((a - x) ^ (b + x) ^ c, i + 1))
            return;
          int J = 0;
          int K = 0;
          if (j) {
            if (!bit::check(a, i))
              J = 1;
          }
          if (k) {
            if (bit::check(b, i))
              K = 1;
          }
          J = J || bit::mask(a, i + 1) <= x;
          K = K || (bit::mask(b, i + 1) + x) >> i;
          chmin(dp[i + 1][J][K], x);
        };
        update(val);
        update(bit::set(val, i));
      }
    }
  }
  int res = inf;
  rep(j, 2) rep(k, 2) { chmin(res, dp[49][j][k]); }
  if (res == inf)
    res = -1;
  cout << res << endl;
  return 0;
}