Problem p01096 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>

using namespace std;

struct Initializer {
  Initializer() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(15);
  }
} initializer;

template <typename T> istream &operator>>(istream &s, vector<T> &v) {
  for (T &t : v)
    s >> t;
  return s;
}

template <typename T> ostream &operator<<(ostream &s, const vector<T> &v) {
  for (const T &t : v)
    s << t << endl;
  return s;
}

template <typename T> T min(vector<T> &v) {
  return *min_element(v.begin(), v.end());
}

template <typename T> T max(vector<T> &v) {
  return *max_element(v.begin(), v.end());
}

template <typename T> int min_element(vector<T> &v) {
  return min_element(v.begin(), v.end()) - v.begin();
}

template <typename T> int max_element(vector<T> &v) {
  return max_element(v.begin(), v.end()) - v.begin();
}

template <typename T> void sort(vector<T> &v) { sort(v.begin(), v.end()); }

template <typename T, typename Function>
void sort(vector<T> &v, Function func) {
  sort(v.begin(), v.end(), func);
}

template <typename T> void rsort(vector<T> &v) { sort(v.rbegin(), v.rend()); }

template <typename T> void reverse(vector<T> &v) {
  reverse(v.begin(), v.end());
}

template <typename T> void unique(vector<T> &v) {
  v.erase(unique(v.begin(), v.end()), v.end());
}

template <typename T> void nth_element(vector<T> &v, int n) {
  nth_element(v.begin(), v.begin() + n, v.end());
}

template <typename T> bool next_permutation(vector<T> &v) {
  return next_permutation(v.begin(), v.end());
}

template <typename T> int find(vector<T> &v, T t) {
  return find(v.begin(), v.end(), t) - v.begin();
}

template <typename T> int in(vector<T> v, T t) {
  return find(v, t) != int(v.size());
}

template <typename T> int lower_bound(vector<T> &v, T t) {
  return lower_bound(v.begin(), v.end(), t) - v.begin();
}

template <typename T> int upper_bound(vector<T> &v, T t) {
  return upper_bound(v.begin(), v.end(), t) - v.begin();
}

template <typename T>
T accumulate(const vector<T> &v, function<T(T, T)> func = plus<T>()) {
  return accumulate(v.begin(), v.end(), T(), func);
}

template <typename T> void adjacent_difference(vector<T> &v) {
  adjacent_difference(v.begin(), v.end(), v.begin());
}

template <typename T> void adjacent_difference(vector<T> &v, vector<T> &u) {
  adjacent_difference(v.begin(), v.end(), u.begin());
}

template <typename T> void partial_sum(vector<T> &v, vector<T> &u) {
  partial_sum(v.begin(), v.end(), u.begin());
}

template <typename T> T inner_product(vector<T> &v, vector<T> &u) {
  return inner_product(v.begin(), v.end(), u.begin(), T(0));
}

template <typename T> int count(const vector<T> &v, T t) {
  return count(v.begin(), v.end(), t);
}

template <typename T, typename Function>
int count_if(const vector<T> &v, Function func) {
  return count_if(v.begin(), v.end(), func);
}

template <typename T, typename Function>
void remove_if(vector<T> &v, Function func) {
  v.erase(remove_if(v.begin(), v.end(), func), v.end());
}

template <typename T, typename Function>
bool all_of(vector<T> v, Function func) {
  return all_of(v.begin(), v.end(), func);
}

template <typename T, typename Function>
bool any_of(vector<T> v, Function func) {
  return any_of(v.begin(), v.end(), func);
}

template <typename T, typename Function>
bool none_of(vector<T> v, Function func) {
  return none_of(v.begin(), v.end(), func);
}

template <typename T> vector<T> subvector(vector<T> &v, int a, int b) {
  return vector<T>(v.begin() + a, v.begin() + b);
}

template <typename T> int kinds(const vector<T> &v) {
  return set<T>(v.begin(), v.end()).size();
}

template <typename T> void iota(vector<T> &v, T t = 0) {
  iota(v.begin(), v.end(), t);
}

template <typename T> bool is_sorted(const vector<T> &v) {
  return is_sorted(v.begin(), v.end());
}

class Solver {
private:
  vector<int> w;
  vector<vector<int>> mem;

public:
  Solver(const vector<int> &w)
      : w(w), mem(w.size() + 1, vector<int>(w.size() + 1, -1)) {}

  int solve(int a, int b) {
    if (b - a < 2)
      return 0;
    if (b - a == 2 && abs(w[a] - w[a + 1]) <= 1)
      return 2;
    if (mem[a][b] != -1)
      return mem[a][b];
    int z = solve(a + 1, b - 1);
    if (z == b - a - 2 && abs(w[a] - w[b - 1]) <= 1)
      z += 2;
    for (int i = a + 1; i < b; ++i) {
      int x = solve(a, i) + solve(i, b);
      if (x > z)
        z = x;
    }
    return mem[a][b] = z;
  }
};

int main() {
  while (true) {
    int n;
    cin >> n;
    if (n == 0)
      break;
    vector<int> w(n);
    cin >> w;
    Solver solver(w);
    cout << solver.solve(0, n) << endl;
  }
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>

using namespace std;

struct Initializer {
  Initializer() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(15);
  }
} initializer;

template <typename T> istream &operator>>(istream &s, vector<T> &v) {
  for (T &t : v)
    s >> t;
  return s;
}

template <typename T> ostream &operator<<(ostream &s, const vector<T> &v) {
  for (const T &t : v)
    s << t << endl;
  return s;
}

template <typename T> T min(vector<T> &v) {
  return *min_element(v.begin(), v.end());
}

template <typename T> T max(vector<T> &v) {
  return *max_element(v.begin(), v.end());
}

template <typename T> int min_element(vector<T> &v) {
  return min_element(v.begin(), v.end()) - v.begin();
}

template <typename T> int max_element(vector<T> &v) {
  return max_element(v.begin(), v.end()) - v.begin();
}

template <typename T> void sort(vector<T> &v) { sort(v.begin(), v.end()); }

template <typename T, typename Function>
void sort(vector<T> &v, Function func) {
  sort(v.begin(), v.end(), func);
}

template <typename T> void rsort(vector<T> &v) { sort(v.rbegin(), v.rend()); }

template <typename T> void reverse(vector<T> &v) {
  reverse(v.begin(), v.end());
}

template <typename T> void unique(vector<T> &v) {
  v.erase(unique(v.begin(), v.end()), v.end());
}

template <typename T> void nth_element(vector<T> &v, int n) {
  nth_element(v.begin(), v.begin() + n, v.end());
}

template <typename T> bool next_permutation(vector<T> &v) {
  return next_permutation(v.begin(), v.end());
}

template <typename T> int find(vector<T> &v, T t) {
  return find(v.begin(), v.end(), t) - v.begin();
}

template <typename T> int in(vector<T> v, T t) {
  return find(v, t) != int(v.size());
}

template <typename T> int lower_bound(vector<T> &v, T t) {
  return lower_bound(v.begin(), v.end(), t) - v.begin();
}

template <typename T> int upper_bound(vector<T> &v, T t) {
  return upper_bound(v.begin(), v.end(), t) - v.begin();
}

template <typename T>
T accumulate(const vector<T> &v, function<T(T, T)> func = plus<T>()) {
  return accumulate(v.begin(), v.end(), T(), func);
}

template <typename T> void adjacent_difference(vector<T> &v) {
  adjacent_difference(v.begin(), v.end(), v.begin());
}

template <typename T> void adjacent_difference(vector<T> &v, vector<T> &u) {
  adjacent_difference(v.begin(), v.end(), u.begin());
}

template <typename T> void partial_sum(vector<T> &v, vector<T> &u) {
  partial_sum(v.begin(), v.end(), u.begin());
}

template <typename T> T inner_product(vector<T> &v, vector<T> &u) {
  return inner_product(v.begin(), v.end(), u.begin(), T(0));
}

template <typename T> int count(const vector<T> &v, T t) {
  return count(v.begin(), v.end(), t);
}

template <typename T, typename Function>
int count_if(const vector<T> &v, Function func) {
  return count_if(v.begin(), v.end(), func);
}

template <typename T, typename Function>
void remove_if(vector<T> &v, Function func) {
  v.erase(remove_if(v.begin(), v.end(), func), v.end());
}

template <typename T, typename Function>
bool all_of(vector<T> v, Function func) {
  return all_of(v.begin(), v.end(), func);
}

template <typename T, typename Function>
bool any_of(vector<T> v, Function func) {
  return any_of(v.begin(), v.end(), func);
}

template <typename T, typename Function>
bool none_of(vector<T> v, Function func) {
  return none_of(v.begin(), v.end(), func);
}

template <typename T> vector<T> subvector(vector<T> &v, int a, int b) {
  return vector<T>(v.begin() + a, v.begin() + b);
}

template <typename T> int kinds(const vector<T> &v) {
  return set<T>(v.begin(), v.end()).size();
}

template <typename T> void iota(vector<T> &v, T t = 0) {
  iota(v.begin(), v.end(), t);
}

template <typename T> bool is_sorted(const vector<T> &v) {
  return is_sorted(v.begin(), v.end());
}

class Solver {
private:
  vector<int> w;
  map<pair<int, int>, int> mem;

public:
  Solver(const vector<int> &w) : w(w) {}

  int solve(int a, int b) {
    if (b - a < 2)
      return 0;
    if (b - a == 2 && abs(w[a] - w[a + 1]) <= 1)
      return 2;
    auto itr = mem.find(make_pair(a, b));
    if (itr != mem.end())
      return itr->second;
    int z = solve(a + 1, b - 1);
    if (z == b - a - 2 && abs(w[a] - w[b - 1]) <= 1)
      z += 2;
    for (int i = a + 1; i < b; ++i) {
      int x = solve(a, i) + solve(i, b);
      if (x > z)
        z = x;
    }
    return mem[make_pair(a, b)] = z;
  }
};

int main() {
  while (true) {
    int n;
    cin >> n;
    if (n == 0)
      break;
    vector<int> w(n);
    cin >> w;
    Solver solver(w);
    cout << solver.solve(0, n) << endl;
  }
}