Problem p03566 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <complex>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <string>
#include <tuple>
#include <utility>
#include <vector>
#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (ll i = ll(a); i < ll(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define all(x) (x).begin(), (x).end()
#define PRINT(V) cout << V << "\n"
#define SORT(V) sort((V).begin(), (V).end())
#define RSORT(V) sort((V).rbegin(), (V).rend())
using namespace std;
using ll = long long;
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
inline void Yes(bool condition) {
  if (condition)
    PRINT("Yes");
  else
    PRINT("No");
}
template <class itr> void cins(itr first, itr last) {
  for (auto i = first; i != last; i++) {
    cin >> (*i);
  }
}
template <class itr> void array_output(itr start, itr goal) {
  string ans = "", k = " ";
  for (auto i = start; i != goal; i++)
    ans += to_string(*i) + k;
  if (!ans.empty())
    ans.pop_back();
  PRINT(ans);
}
ll gcd(ll a, ll b) { return a ? gcd(b % a, a) : b; }
const int INF = 1e9;
const ll MOD = 1000000007;
typedef pair<ll, ll> P;
const ll MAX = 20000;
constexpr ll nx[4] = {1, 0, -1, 0};
constexpr ll ny[4] = {0, 1, 0, -1};

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  vector<ll> t(n), v(n);
  cins(all(t));
  cins(all(v));
  vector<vector<double>> dp(20005, vector<double>(205, 0));
  int now = 0;
  rep(i, n) {
    rep(j, 1, 2 * t[i] + 1) {
      int limit = 2 * v[i];
      rep(k, 201) {
        if ((i != 0 || k != 0) && dp[now + j - 1][k] == 0.0)
          continue;
        if (i != 0 && j == 1) {
          if (k > limit)
            continue;
        }
        if (k == 0) {
          dp[now + j][0] = dp[now + j - 1][0];
          if (1 <= limit)
            dp[now + j][1] = dp[now + j - 1][0] + 0.125;
        } else if (k == 200) {
          if (200 <= limit)
            chmax(dp[now + j][200], dp[now + j - 1][200] + 50);
          if (199 <= limit)
            chmax(dp[now + j][199], dp[now + j - 1][200] + (2 * k - 1) / 8.0);
        } else {
          if (k - 1 <= limit)
            chmax(dp[now + j][k - 1], dp[now + j - 1][k] + (2 * k - 1) / 8.0);
          if (k <= limit)
            chmax(dp[now + j][k], dp[now + j - 1][k] + k / 4.0);
          if (k + 1 <= limit)
            chmax(dp[now + j][k + 1], dp[now + j - 1][k] + (2 * k + 1) / 8.0);
        }
      }
    }
    now += 2 * t[i];
  }
  printf("%0.10f\n", dp[now][0]);
}


Fixed submission:
#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <complex>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <string>
#include <tuple>
#include <utility>
#include <vector>
#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (ll i = ll(a); i < ll(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define all(x) (x).begin(), (x).end()
#define PRINT(V) cout << V << "\n"
#define SORT(V) sort((V).begin(), (V).end())
#define RSORT(V) sort((V).rbegin(), (V).rend())
using namespace std;
using ll = long long;
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
inline void Yes(bool condition) {
  if (condition)
    PRINT("Yes");
  else
    PRINT("No");
}
template <class itr> void cins(itr first, itr last) {
  for (auto i = first; i != last; i++) {
    cin >> (*i);
  }
}
template <class itr> void array_output(itr start, itr goal) {
  string ans = "", k = " ";
  for (auto i = start; i != goal; i++)
    ans += to_string(*i) + k;
  if (!ans.empty())
    ans.pop_back();
  PRINT(ans);
}
ll gcd(ll a, ll b) { return a ? gcd(b % a, a) : b; }
const int INF = 1e9;
const ll MOD = 1000000007;
typedef pair<ll, ll> P;
const ll MAX = 20000;
constexpr ll nx[4] = {1, 0, -1, 0};
constexpr ll ny[4] = {0, 1, 0, -1};

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  vector<ll> t(n), v(n);
  cins(all(t));
  cins(all(v));
  vector<vector<double>> dp(40005, vector<double>(205, 0));
  int now = 0;
  rep(i, n) {
    rep(j, 1, 2 * t[i] + 1) {
      int limit = 2 * v[i];
      rep(k, 201) {
        if ((i != 0 || k != 0) && dp[now + j - 1][k] == 0.0)
          continue;
        if (i != 0 && j == 1) {
          if (k > limit)
            continue;
        }
        if (k == 0) {
          dp[now + j][0] = dp[now + j - 1][0];
          if (1 <= limit)
            dp[now + j][1] = dp[now + j - 1][0] + 0.125;
        } else if (k == 200) {
          if (200 <= limit)
            chmax(dp[now + j][200], dp[now + j - 1][200] + 50);
          if (199 <= limit)
            chmax(dp[now + j][199], dp[now + j - 1][200] + (2 * k - 1) / 8.0);
        } else {
          if (k - 1 <= limit)
            chmax(dp[now + j][k - 1], dp[now + j - 1][k] + (2 * k - 1) / 8.0);
          if (k <= limit)
            chmax(dp[now + j][k], dp[now + j - 1][k] + k / 4.0);
          if (k + 1 <= limit)
            chmax(dp[now + j][k + 1], dp[now + j - 1][k] + (2 * k + 1) / 8.0);
        }
      }
    }
    now += 2 * t[i];
  }
  printf("%0.10f\n", dp[now][0]);
}