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

#include <bits/stdc++.h>
using namespace std;

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

template <typename T, typename U>
istream &operator>>(istream &istr, pair<T, U> &p) {
  istr >> p.first >> p.second;
  return istr;
}

template <typename T> ostream &operator<<(ostream &ostr, vector<T> &v) {
  if (!v.empty()) {
    ostr << v.front();
    for (auto itr = ++v.begin(); itr != v.end(); itr++)
      // ostr << *itr;
      ostr << " " << *itr;
  }
  return ostr;
}

template <typename T, typename U>
ostream &operator<<(ostream &ostr, pair<T, U> &p) {
  // ostr << p.first << p.second;
  // ostr << p.first << ", " << p.second;
  ostr << "(" << p.first << ", " << p.second << ")";
  return ostr;
}

template <typename T>
ostream &operator<<(ostream &ostr, vector<vector<T>> &vv) {
  if (!vv.empty()) {
    ostr << vv.front();
    for (auto itr = ++vv.begin(); itr != vv.end(); itr++)
      ostr << endl << *itr;
  }
  return ostr;
}

template <typename T, typename U>
ostream &operator<<(ostream &ostr, vector<pair<T, U>> &vp) {
  if (!vp.empty()) {
    ostr << vp.front();
    for (auto itr = ++vp.begin(); itr != vp.end(); itr++)
      ostr << endl << *itr;
  }
  return ostr;
}

typedef long long ll;
typedef vector<ll> vll;
typedef vector<char> vc;
typedef vector<double> vd;
// vll v(n); v[i]=x;
typedef vector<vll> vvll;
typedef vector<vc> vvc;
typedef vector<vd> vvd;
// vvll v(m,vll(n)); v[i][j]=x;
typedef pair<ll, ll> pll;
typedef pair<double, double> pd;
typedef vector<pll> vpll;
typedef vector<pd> vpd;
// vpll v(n); v[i]=make_pair(x,y); v[i].first/second;
// v.front() : v[0]
// v.back()  : v[v.size()-1]

#define PI 3.1415926535897932
#define EPS 1e-12
#define INF ((ll)1e+12)
#define REP(i, n) for (ll i = 0; i < (n); i++)
#define RREP(i, n) for (ll i = (n)-1; i >= 0; i--)
#define FOR(i, a, b) for (ll i = (a); i <= (b); i++)
#define FORR(i, a, b) for (ll i = (b); i >= (a); i--)
#define fix(x) cout << fixed << setprecision(x)
#define dump(x) cout << #x << " = " << (x) << endl
#define all(x) (x).begin(), (x).end()

template <typename T> T sum(vector<T> &v) { return accumulate(all(v), (T)0); }
template <typename T> inline void sort(vector<T> &v) { sort(all(v)); }
template <typename T> inline void rsort(vector<T> &v) {
  sort(all(v), greater<T>());
}
template <typename T> inline void chmin(T &a, T b) {
  if (a > b)
    a = b;
}
template <typename T> inline void chmax(T &a, T b) {
  if (a < b)
    a = b;
}

int main() {
  ll n, ans = 0;
  cin >> n;
  vll a(n);
  map<ll, ll> l;

  cin >> a;
  REP(i, n) l[i + 1 + a[i]]++;
  // for(auto& [key, val] : l) cout << key << "=>" << val << endl;
  REP(i, n) {
    if (l[i + 1 - a[i]] > 0)
      ans += l[i + 1 - a[i]];
  }
  cout << ans << endl;
  return 0;
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;

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

template <typename T, typename U>
istream &operator>>(istream &istr, pair<T, U> &p) {
  istr >> p.first >> p.second;
  return istr;
}

template <typename T> ostream &operator<<(ostream &ostr, vector<T> &v) {
  if (!v.empty()) {
    ostr << v.front();
    for (auto itr = ++v.begin(); itr != v.end(); itr++)
      // ostr << *itr;
      ostr << " " << *itr;
  }
  return ostr;
}

template <typename T, typename U>
ostream &operator<<(ostream &ostr, pair<T, U> &p) {
  // ostr << p.first << p.second;
  // ostr << p.first << ", " << p.second;
  ostr << "(" << p.first << ", " << p.second << ")";
  return ostr;
}

template <typename T>
ostream &operator<<(ostream &ostr, vector<vector<T>> &vv) {
  if (!vv.empty()) {
    ostr << vv.front();
    for (auto itr = ++vv.begin(); itr != vv.end(); itr++)
      ostr << endl << *itr;
  }
  return ostr;
}

template <typename T, typename U>
ostream &operator<<(ostream &ostr, vector<pair<T, U>> &vp) {
  if (!vp.empty()) {
    ostr << vp.front();
    for (auto itr = ++vp.begin(); itr != vp.end(); itr++)
      ostr << endl << *itr;
  }
  return ostr;
}

typedef long long ll;
typedef vector<ll> vll;
typedef vector<char> vc;
typedef vector<double> vd;
// vll v(n); v[i]=x;
typedef vector<vll> vvll;
typedef vector<vc> vvc;
typedef vector<vd> vvd;
// vvll v(m,vll(n)); v[i][j]=x;
typedef pair<ll, ll> pll;
typedef pair<double, double> pd;
typedef vector<pll> vpll;
typedef vector<pd> vpd;
// vpll v(n); v[i]=make_pair(x,y); v[i].first/second;
// v.front() : v[0]
// v.back()  : v[v.size()-1]

#define PI 3.1415926535897932
#define EPS 1e-12
#define INF ((ll)1e+12)
#define REP(i, n) for (ll i = 0; i < (n); i++)
#define RREP(i, n) for (ll i = (n)-1; i >= 0; i--)
#define FOR(i, a, b) for (ll i = (a); i <= (b); i++)
#define FORR(i, a, b) for (ll i = (b); i >= (a); i--)
#define fix(x) cout << fixed << setprecision(x)
#define dump(x) cout << #x << " = " << (x) << endl
#define all(x) (x).begin(), (x).end()

template <typename T> T sum(vector<T> &v) { return accumulate(all(v), (T)0); }
template <typename T> inline void sort(vector<T> &v) { sort(all(v)); }
template <typename T> inline void rsort(vector<T> &v) {
  sort(all(v), greater<T>());
}
template <typename T> inline void chmin(T &a, T b) {
  if (a > b)
    a = b;
}
template <typename T> inline void chmax(T &a, T b) {
  if (a < b)
    a = b;
}

int main() {
  ll n, ans = 0;
  cin >> n;
  vvll b(n);

  REP(i, n) {
    ll a, c = 1;
    cin >> a;
    REP(j, b[i].size()) {
      if (a == b[i][j])
        ans++;
    }
    FOR(j, i + a + 1, n - 1) {
      b[j].emplace_back(c);
      c++;
    }
  }
  // cout << b << endl;
  cout << ans << endl;
  return 0;
}