Problem p02691 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#define len(X) ((int)(X).size())

#ifdef __LOCAL
#define DBG(X) cout << #X << "=" << (X) << '\\n';
#define SAY(X) cout << (X) << '\\n';
#else
#define DBG(X)
#define SAY(X)
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

const int INT_INF = (int)(2e9);
const ll LL_INF = (ll)(2e18);

const int NIL = -1;
static mt19937 _g(time(nullptr));

std::string pad(int num) {
  char buffer[4];
  std::snprintf(buffer, sizeof(buffer), "%03d", num);
  return buffer;
}

inline ll randint(ll a, ll b) {
  ll w = (_g() << 31LL) ^ _g();
  return a + w % (b - a + 1);
}
inline void fast_io() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
};
template <typename T> inline T sign(T x) { return T(x > 0) - T(x < 0); }
template <typename T, typename S>
inline ostream &operator<<(ostream &os, const pair<T, S> p) {
  cout << "[" << p.first << ";" << p.second << "]";
  return os;
}
template <typename T>
inline ostream &operator<<(ostream &os, const vector<T> &v) {
  for (auto el : v)
    cout << el << " ";
  return os;
}
template <typename T> inline T fetch() {
  T ret;
  cin >> ret;
  return ret;
}
template <typename T> inline vector<T> fetch_vec(int sz) {
  vector<T> ret(sz);
  for (auto &elem : ret)
    cin >> elem;
  return ret;
}

#ifdef _MSC_VER
#include <intrin.h>
#define __builtin_popcount __popcnt
#endif

ll solve() {
  int N;

  std::cin >> N;

  vector<int> v = fetch_vec<int>(N);
  unordered_map<int, int> vplus;

  ll counter = 0;

  for (int i = 0; i < N; ++i) {
    counter += vplus[i - v[i]];
    vplus[v[i] + i]++;
  }

  return counter;
}

int main() {
  std::cout << solve() << std::endl;
  //    solve();

  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#define len(X) ((int)(X).size())

#ifdef __LOCAL
#define DBG(X) cout << #X << "=" << (X) << '\\n';
#define SAY(X) cout << (X) << '\\n';
#else
#define DBG(X)
#define SAY(X)
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

const int INT_INF = (int)(2e9);
const ll LL_INF = (ll)(2e18);

const int NIL = -1;
static mt19937 _g(time(nullptr));

std::string pad(int num) {
  char buffer[4];
  std::snprintf(buffer, sizeof(buffer), "%03d", num);
  return buffer;
}

inline ll randint(ll a, ll b) {
  ll w = (_g() << 31LL) ^ _g();
  return a + w % (b - a + 1);
}
inline void fast_io() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
};
template <typename T> inline T sign(T x) { return T(x > 0) - T(x < 0); }
template <typename T, typename S>
inline ostream &operator<<(ostream &os, const pair<T, S> p) {
  cout << "[" << p.first << ";" << p.second << "]";
  return os;
}
template <typename T>
inline ostream &operator<<(ostream &os, const vector<T> &v) {
  for (auto el : v)
    cout << el << " ";
  return os;
}
template <typename T> inline T fetch() {
  T ret;
  cin >> ret;
  return ret;
}
template <typename T> inline vector<T> fetch_vec(int sz) {
  vector<T> ret(sz);
  for (auto &elem : ret)
    cin >> elem;
  return ret;
}

#ifdef _MSC_VER
#include <intrin.h>
#define __builtin_popcount __popcnt
#endif

int solve() {
  int N;

  std::cin >> N;

  vector<int> v = fetch_vec<int>(N);
  vector<int> vm = v;

  for (int i = vm.size() - 2; i >= 0; --i) {
    if (vm[i] < vm[i + 1])
      vm[i] = vm[i + 1];
  }

  ll counter = 0;

  for (int i = 0; i < N; ++i) {

    for (int j = i + v[i] + 1; j < N; ++j) {
      if (v[i] + v[j] == j - i)
        ++counter;

      if (vm[j] < j - i - v[i])
        break;
    }
  }

  return counter;
}

int main() {
  std::cout << solve() << std::endl;
  //    solve();

  return 0;
}