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

#pragma region template
#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>

#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define rep(i, n) for (ll i = 0, i##_len = (n); i < i##_len; i++)
#define brep(i, a, b) for (ll i = (a), i##_len = (b); i <= i##_len; i++)
#define rrep(i, n)                                                             \\
  ll i = (n);                                                                  \\
  ll now = -1;                                                                 \\
  while (i-- && (now++ || 1))
#define xrep(i, n) for (ll i = 1, i##_len = (n); i <= i##_len; i++)
#define Yes(n) cout << ((n) ? YES : NO) << '\\n'
#define rYes(n)                                                                \\
  cout << ((n) ? YES : NO) << '\\n';                                            \\
  return
#define Sort(v) sort(all(v))
#define rSort(v)                                                               \\
  sort(all(v));                                                                \\
  reverse(all(v))
#define Unique(v) (v).erase(unique(all(v)), (v).end())
#define eb emplace_back

using namespace std;
using ll = long long;
using vll = vector<ll>;
using vbl = vector<bool>;
using vint = vector<int>;
using vvll = vector<vll>;
using vstr = vector<string>;

// --- functions which take 1 argument ---
static inline void ignore_ret(int x) { x++; }
template <class T> inline int sgn(T x) { return (x > 0) - (x < 0); }
template <class T> inline ll factorial(T n) {
  if (n == 0)
    return 1;
  ll r = 1;
  for (T i = 2; i <= n; i++)
    r *= i;
  return r;
}
template <class T> inline map<T, T> factorize(T n) {
  map<T, T> r;
  for (T i = 2; i * i <= n; i++) {
    while (n % i == 0) {
      r[i]++;
      n /= i;
    }
  }
  if (n != 1)
    r[n] = 1;
  return r;
}

// --- functions which take 2 arguments ---
template <class T> inline bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline T nPr(T n, T k) {
  if (n < k || n < 0 || k < 0)
    return 0;
  T r = 1;
  for (T i = n - k + 1; i <= n; i++)
    r *= i;
  return r;
}
template <class T> inline T nCr(T n, T k) {
  if (n < k || n < 0 || k < 0)
    return 0;
  T r = 1;
  k = min(k, n - k);
  for (T i = n - k + 1; i <= n; i++)
    r *= i;
  return r / factorial(k);
}

// --- functions which take vector(s) as argument(s) ---
template <class T> inline void print(T v) {
  cout << "[ ";
  for (auto x : v)
    cout << x << ' ';
  cout << "]\\n";
}
template <class T> inline void print_d(T v) {
  for (auto x : v)
    cout << x;
  cout << '\\n';
}
template <class T> inline T min(vector<T> v) { return *min_element(all(v)); }
template <class T> inline T max(vector<T> v) { return *max_element(all(v)); }
template <class T> inline ll sum(T v) { return reduce(all(v), 0LL); }
template <class T> inline T gcd(vector<T> v) {
  T r = v[0];
  for (T i = 1; i < v.size(); i++)
    r = gcd(r, v[i]);
  return r;
}
template <class T> inline T lcm(vector<T> v) {
  T r = v[0];
  for (T i = 1; i < v.size(); i++)
    r = lcm(r, v[i]);
  return r;
}
template <class T> inline double abs(T v) {
  return sqrt(reduce(all(v), 0.0, [](int s, int v) { return s += v * v; }));
}
template <class T> inline T vector_add(T u, T v) {
  ll s = u.size();
  if (s > v.size())
    return {};
  T r;
  rep(i, s) r.eb(u[i] + v[i]);
  return r;
}
template <class T> inline T vector_subtract(T u, T v) {
  ll s = u.size();
  if (s > v.size())
    return {};
  T r;
  rep(i, s) r.eb(u[i] - v[i]);
  return r;
}
template <class T> inline T dot_product(vector<T> u, vector<T> v) {
  if (u.size() < v.size())
    return 0;
  T r = 0;
  for (T i = 0; i < u.size(); i++)
    r += u[i] * v[i];
  return r;
}
template <class T> inline T cross_product(T u, T v) {
  T r(3);
  r[0] = u[1] * v[2] - u[2] * v[1];
  r[1] = u[2] * v[0] - u[0] * v[2];
  r[2] = u[0] * v[1] - u[1] * v[0];
  return r;
}

// --- functions which take set(s) as argument(s) ---
template <class T> inline T min(set<T> v) { return *min_element(all(v)); }
template <class T> inline T max(set<T> v) { return *max_element(all(v)); }
template <class T> inline T gcd(set<T> v) {
  T r = v[0];
  for (T i = 1; i < v.size(); i++)
    r = gcd(r, v[i]);
  return r;
}
template <class T> inline T lcm(set<T> v) {
  T r = v[0];
  for (T i = 1; i < v.size(); i++)
    r = lcm(r, v[i]);
  return r;
}
template <class T> inline T dot_product(set<T> u, set<T> v) {
  if (u.size() < v.size())
    return 0;
  T r = 0;
  for (T i = 0; i < u.size(); i++)
    r += u[i] * v[i];
  return r;
}

// --- Template ends here ---
#pragma endregion template

int main() {
  int N;
  cin >> N;
  vint A(N);
  for (int i = 0; i < N; i++)
    cin >> A[i];

  map<int, int> L, R;
  for (int i = 0; i < N; i++) {
    L[i + A[i]]++;
    R[i - A[i]]++;
  }

  ll ans = 0;
  for (auto [l, v1] : L) {
    ans += (ll)v1 * R[l];
  }

  cout << ans << endl;
  return 0;
}


Error: TLE

Fixed submission:

#pragma region template
#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>

#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define rep(i, n) for (ll i = 0, i##_len = (n); i < i##_len; i++)
#define brep(i, a, b) for (ll i = (a), i##_len = (b); i <= i##_len; i++)
#define rrep(i, n)                                                             \\
  ll i = (n);                                                                  \\
  ll now = -1;                                                                 \\
  while (i-- && (now++ || 1))
#define xrep(i, n) for (ll i = 1, i##_len = (n); i <= i##_len; i++)
#define Yes(n) cout << ((n) ? YES : NO) << '\\n'
#define rYes(n)                                                                \\
  cout << ((n) ? YES : NO) << '\\n';                                            \\
  return
#define Sort(v) sort(all(v))
#define rSort(v)                                                               \\
  sort(all(v));                                                                \\
  reverse(all(v))
#define Unique(v) (v).erase(unique(all(v)), (v).end())
#define eb emplace_back

using namespace std;
using ll = long long;
using vll = vector<ll>;
using vbl = vector<bool>;
using vint = vector<int>;
using vvll = vector<vll>;
using vstr = vector<string>;

// --- functions which take 1 argument ---
static inline void ignore_ret(int x) { x++; }
template <class T> inline int sgn(T x) { return (x > 0) - (x < 0); }
template <class T> inline ll factorial(T n) {
  if (n == 0)
    return 1;
  ll r = 1;
  for (T i = 2; i <= n; i++)
    r *= i;
  return r;
}
template <class T> inline map<T, T> factorize(T n) {
  map<T, T> r;
  for (T i = 2; i * i <= n; i++) {
    while (n % i == 0) {
      r[i]++;
      n /= i;
    }
  }
  if (n != 1)
    r[n] = 1;
  return r;
}

// --- functions which take 2 arguments ---
template <class T> inline bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline T nPr(T n, T k) {
  if (n < k || n < 0 || k < 0)
    return 0;
  T r = 1;
  for (T i = n - k + 1; i <= n; i++)
    r *= i;
  return r;
}
template <class T> inline T nCr(T n, T k) {
  if (n < k || n < 0 || k < 0)
    return 0;
  T r = 1;
  k = min(k, n - k);
  for (T i = n - k + 1; i <= n; i++)
    r *= i;
  return r / factorial(k);
}

// --- functions which take vector(s) as argument(s) ---
template <class T> inline void print(T v) {
  cout << "[ ";
  for (auto x : v)
    cout << x << ' ';
  cout << "]\\n";
}
template <class T> inline void print_d(T v) {
  for (auto x : v)
    cout << x;
  cout << '\\n';
}
template <class T> inline T min(vector<T> v) { return *min_element(all(v)); }
template <class T> inline T max(vector<T> v) { return *max_element(all(v)); }
template <class T> inline ll sum(T v) { return reduce(all(v), 0LL); }
template <class T> inline T gcd(vector<T> v) {
  T r = v[0];
  for (T i = 1; i < v.size(); i++)
    r = gcd(r, v[i]);
  return r;
}
template <class T> inline T lcm(vector<T> v) {
  T r = v[0];
  for (T i = 1; i < v.size(); i++)
    r = lcm(r, v[i]);
  return r;
}
template <class T> inline double abs(T v) {
  return sqrt(reduce(all(v), 0.0, [](int s, int v) { return s += v * v; }));
}
template <class T> inline T vector_add(T u, T v) {
  ll s = u.size();
  if (s > v.size())
    return {};
  T r;
  rep(i, s) r.eb(u[i] + v[i]);
  return r;
}
template <class T> inline T vector_subtract(T u, T v) {
  ll s = u.size();
  if (s > v.size())
    return {};
  T r;
  rep(i, s) r.eb(u[i] - v[i]);
  return r;
}
template <class T> inline T dot_product(vector<T> u, vector<T> v) {
  if (u.size() < v.size())
    return 0;
  T r = 0;
  for (T i = 0; i < u.size(); i++)
    r += u[i] * v[i];
  return r;
}
template <class T> inline T cross_product(T u, T v) {
  T r(3);
  r[0] = u[1] * v[2] - u[2] * v[1];
  r[1] = u[2] * v[0] - u[0] * v[2];
  r[2] = u[0] * v[1] - u[1] * v[0];
  return r;
}

// --- functions which take set(s) as argument(s) ---
template <class T> inline T min(set<T> v) { return *min_element(all(v)); }
template <class T> inline T max(set<T> v) { return *max_element(all(v)); }
template <class T> inline T gcd(set<T> v) {
  T r = v[0];
  for (T i = 1; i < v.size(); i++)
    r = gcd(r, v[i]);
  return r;
}
template <class T> inline T lcm(set<T> v) {
  T r = v[0];
  for (T i = 1; i < v.size(); i++)
    r = lcm(r, v[i]);
  return r;
}
template <class T> inline T dot_product(set<T> u, set<T> v) {
  if (u.size() < v.size())
    return 0;
  T r = 0;
  for (T i = 0; i < u.size(); i++)
    r += u[i] * v[i];
  return r;
}

// --- Template ends here ---
#pragma endregion template

int main() {
  int N;
  cin >> N;
  vint A(N);
  for (int i = 0; i < N; i++)
    cin >> A[i];

  map<int, int> L, R;
  for (int i = 0; i < N; i++) {
    L[i + A[i]]++;
    R[i - A[i]]++;
  }

  long long ans = 0;
  for (auto [l, v1] : L) {
    for (auto [r, v2] : R) {
      if (l < r)
        break;
      ans += (l == r) * (long long)v1 * v2;
    }
  }

  cout << ans << endl;
  return 0;
}