Problem p03173 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <iomanip>
#include <iostream>
#include <string.h>
#include <vector>
using namespace std;
#define mod (long)(1e9 + 7)
#define all(x) (x).begin(), (x).end()
#define bitcount(n) __builtin_popcountl(long(n))
#define fcout cout << fixed << setprecision(15)
#define highest(x) (63 - __builtin_clzl(x))
#define long long long
template <class T> inline void YES(T condition) {
  if (condition)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
template <class T> inline void Yes(T condition) {
  if (condition)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
template <class T> inline void POSS(T condition) {
  if (condition)
    cout << "POSSIBLE" << endl;
  else
    cout << "IMPOSSIBLE" << endl;
}
template <class T> inline void Poss(T condition) {
  if (condition)
    cout << "Possible" << endl;
  else
    cout << "Impossible" << endl;
}
template <class T> inline void First(T condition) {
  if (condition)
    cout << "First" << endl;
  else
    cout << "Second" << endl;
}
template <class T = string, class U = char>
int character_count(T text, U character) {
  int ans = 0;
  for (U i : text) {
    ans += (i == character);
  }
  return ans;
}
long power(long base, long exponent, long module) {
  if (exponent % 2) {
    return power(base, exponent - 1, module) * base % module;
  } else if (exponent) {
    long root_ans = power(base, exponent / 2, module);
    return root_ans * root_ans % module;
  } else {
    return 1;
  }
}
struct position {
  int y, x;
};
position move_pattern[4] = {
    {-1, 0},
    {0, 1},
    {1, 0},
    {0, -1}}; // double euclidean(position first, position second){ return
              // sqrt((second.x - first.x) * (second.x - first.x) + (second.y -
              // first.y) * (second.y - first.y)); }
template <class T, class U> string to_string(pair<T, U> x) {
  return to_string(x.first) + "," + to_string(x.second);
}
template <class itr> void array_output(itr start, itr goal) {
  string ans;
  for (auto i = start; i != goal; i++) {
    ans += to_string(*i) + " ";
  }
  ans.pop_back();
  cout << ans << endl;
}
template <class itr> void cins(itr start, itr goal) {
  for (auto i = start; i != goal; i++) {
    cin >> (*i);
  }
}
template <class T> T gcd(T a, T b) {
  if (a && b) {
    return gcd(min(a, b), max(a, b) % min(a, b));
  } else {
    return a;
  }
}
template <class T> T lcm(T a, T b) { return a / gcd(a, b) * b; }
struct combination {
  vector<long> fact, inv;
  combination(int sz) : fact(sz + 1), inv(sz + 1) {
    fact[0] = 1;
    for (int i = 1; i <= sz; i++) {
      fact[i] = fact[i - 1] * i % mod;
    }
    inv[sz] = power(fact[sz], mod - 2, mod);
    for (int i = sz - 1; i >= 0; i--) {
      inv[i] = inv[i + 1] * (i + 1) % mod;
    }
  }
  long C(int p, int q) const {
    if (q < 0 || p < q)
      return 0;
    return (fact[p] * inv[q] % mod * inv[p - q] % mod);
  }
};

int N;
vector<long> a_sum;

long dp[404][404];

long decompose(int l, int r) {
  if (l + 1 == r) {
    return 0;
  }
  long ans = 1e18;
  for (int i = l + 1; i < r; i++) {
    ans = min(ans, decompose(l, i) + decompose(i, r));
  }
  return dp[l][r] = ans + a_sum[r] - a_sum[l];
}

int main() {
  cin >> N;
  a_sum.resize(N + 1, 0);
  for (int i = 0; i < N; i++) {
    int a;
    cin >> a;
    a_sum[i + 1] = a_sum[i] + a;
  }
  memset(dp, -1, sizeof(dp));
  cout << decompose(0, N) << endl;
}


Fixed submission:
#include <algorithm>
#include <iomanip>
#include <iostream>
#include <string.h>
#include <vector>
using namespace std;
#define mod (long)(1e9 + 7)
#define all(x) (x).begin(), (x).end()
#define bitcount(n) __builtin_popcountl(long(n))
#define fcout cout << fixed << setprecision(15)
#define highest(x) (63 - __builtin_clzl(x))
#define long long long
template <class T> inline void YES(T condition) {
  if (condition)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
template <class T> inline void Yes(T condition) {
  if (condition)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
template <class T> inline void POSS(T condition) {
  if (condition)
    cout << "POSSIBLE" << endl;
  else
    cout << "IMPOSSIBLE" << endl;
}
template <class T> inline void Poss(T condition) {
  if (condition)
    cout << "Possible" << endl;
  else
    cout << "Impossible" << endl;
}
template <class T> inline void First(T condition) {
  if (condition)
    cout << "First" << endl;
  else
    cout << "Second" << endl;
}
template <class T = string, class U = char>
int character_count(T text, U character) {
  int ans = 0;
  for (U i : text) {
    ans += (i == character);
  }
  return ans;
}
long power(long base, long exponent, long module) {
  if (exponent % 2) {
    return power(base, exponent - 1, module) * base % module;
  } else if (exponent) {
    long root_ans = power(base, exponent / 2, module);
    return root_ans * root_ans % module;
  } else {
    return 1;
  }
}
struct position {
  int y, x;
};
position move_pattern[4] = {
    {-1, 0},
    {0, 1},
    {1, 0},
    {0, -1}}; // double euclidean(position first, position second){ return
              // sqrt((second.x - first.x) * (second.x - first.x) + (second.y -
              // first.y) * (second.y - first.y)); }
template <class T, class U> string to_string(pair<T, U> x) {
  return to_string(x.first) + "," + to_string(x.second);
}
template <class itr> void array_output(itr start, itr goal) {
  string ans;
  for (auto i = start; i != goal; i++) {
    ans += to_string(*i) + " ";
  }
  ans.pop_back();
  cout << ans << endl;
}
template <class itr> void cins(itr start, itr goal) {
  for (auto i = start; i != goal; i++) {
    cin >> (*i);
  }
}
template <class T> T gcd(T a, T b) {
  if (a && b) {
    return gcd(min(a, b), max(a, b) % min(a, b));
  } else {
    return a;
  }
}
template <class T> T lcm(T a, T b) { return a / gcd(a, b) * b; }
struct combination {
  vector<long> fact, inv;
  combination(int sz) : fact(sz + 1), inv(sz + 1) {
    fact[0] = 1;
    for (int i = 1; i <= sz; i++) {
      fact[i] = fact[i - 1] * i % mod;
    }
    inv[sz] = power(fact[sz], mod - 2, mod);
    for (int i = sz - 1; i >= 0; i--) {
      inv[i] = inv[i + 1] * (i + 1) % mod;
    }
  }
  long C(int p, int q) const {
    if (q < 0 || p < q)
      return 0;
    return (fact[p] * inv[q] % mod * inv[p - q] % mod);
  }
};

int N;
vector<long> a_sum;

long dp[404][404];

long decompose(int l, int r) {
  if (l + 1 == r) {
    return 0;
  } else if (dp[l][r] != -1) {
    return dp[l][r];
  }
  long ans = 1e18;
  for (int i = l + 1; i < r; i++) {
    ans = min(ans, decompose(l, i) + decompose(i, r));
  }
  return dp[l][r] = ans + a_sum[r] - a_sum[l];
}

int main() {
  cin >> N;
  a_sum.resize(N + 1, 0);
  for (int i = 0; i < N; i++) {
    int a;
    cin >> a;
    a_sum[i + 1] = a_sum[i] + a;
  }
  memset(dp, -1, sizeof(dp));
  cout << decompose(0, N) << endl;
}