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

/*#include <boost/multiprecision/cpp_dec_float.hpp>
#include <boost/multiprecision/cpp_int.hpp>

#include <boost/rational.hpp>
*/
#include <bits/stdc++.h>
using namespace std;
#define _GLIBCXX_DEBUG
#define rep(i, t) for (ll i = (ll)(0); i < (ll)(t); i++)
#define rep2(i, s, t) for (ll i = (ll)(s); i < (ll)(t); i++)
#define rep3(i, t) for (ll i = (ll)(1); i <= (ll)(t); i++)
#define rep4(i, s, t) for (ll i = (ll)(s); i <= (ll)(t); i++)
#define repr(i, t) for (ll i = (t - 1); i >= (0); i--)
#define repr2(i, s, t) for (ll i = (t - 1); i >= (s); i--)
#define repr3(i, t) for (ll i = (t); i >= (1); i--)
#define repr4(i, s, t) for (ll i = (t); i >= (s); i--)
using ll = long long;
using ld = long double;
using ull = unsigned long long;
using uint = unsigned;
using pcc = pair<char, char>;
using pll = pair<ll, ll>;
using pii = pair<int, int>;
using pdd = pair<double, double>;
using tuplis = array<ll, 3>;
template <class T> using pq = priority_queue<T, vector<T>, greater<T>>;
const ll LINF = 0x1fffffffffffffff;
const ll MINF = 0x7fffffffffff;
const int INF = 0x3fffffff;
const int mod = 1000000007;
const int MODD = 998244353;
const ld DINF = numeric_limits<ld>::infinity();
const ld EPS = 1e-9;
const ld PI = acos(-1);
const ll dx[] = {0, 1, 0, -1, 1, -1, 1, -1};
const ll dy[] = {1, 0, -1, 0, 1, 1, -1, -1};
#define is_low(c) ('a' <= c) && (c <= 'z')
#define is_upp(c) ('A' <= c) && (c <= 'Z')
#define each1(i, a) for (auto &&i : a)
#define each2(x, y, a) for (auto &&[x, y] : a)
#define each3(x, y, z, a) for (auto &&[x, y, z] : a)
#define rrep(n) for (ll i = (n); i--;)
#define stlen(s) ll s.size() - 1
#define all(v) begin(v), end(v)
#define range(v, a) begin(v), begin(v) + a
#define range2(v, a, b) begin(v) + a, begin(v) + b
#define range3(v, a) begin(v) + 1, begin(v) + a + 1
#define range4(v, a, b) begin(v) + a + 1, begin(v) + b + 1
#define allr(v) rbegin(v), v.rend(v)
#define ranger(v, a) rbegin(v), rbegin(v) + a
#define ranger2(v, a, b) rbegin(v) + a, rbegin(v) + b
#define ranger3(v, a) rbegin(v) + 1, rbegin(v) + a + 1
#define ranger4(v, a, b) rbegin(v) + a + 1, rbegin(v) + b + 1
#define cout(n) cout << std::fixed << std::setprecision(n)
// #define sum(...) accumulate(all(__VA_ARGS__),0LL)
#define dsum(...) accumulate(all(__VA_ARGS__), 0.0L)
#define elif else if
#define unless(a) if (!(a))
#define mp make_pair
#define mt make_tuple
#define INT(...)                                                               \\
  int __VA_ARGS__;                                                             \\
  in(__VA_ARGS__)
#define LL(...)                                                                \\
  ll __VA_ARGS__;                                                              \\
  in(__VA_ARGS__)
#define ULL(...)                                                               \\
  ull __VA_ARGS__;                                                             \\
  in(__VA_ARGS__)
#define STR(...)                                                               \\
  string __VA_ARGS__;                                                          \\
  in(__VA_ARGS__)
#define CHR(...)                                                               \\
  char __VA_ARGS__;                                                            \\
  in(__VA_ARGS__)
#define DBL(...)                                                               \\
  double __VA_ARGS__;                                                          \\
  in(__VA_ARGS__)
#define LD(...)                                                                \\
  ld __VA_ARGS__;                                                              \\
  in(__VA_ARGS__)
#define Sort(a) sort(all(a))
#define Rev(a) reverse(all(a))
#define Uniq(a)                                                                \\
  sort(all(a)); a.erase(unique(all(a))),end(a))
#define vec(type, name, ...) vector<type> name(__VA_ARGS__)
#define VEC(type, name, size)                                                  \\
  vector<type> name(size);                                                     \\
  in(name)
#define vv(type, name, h, ...)                                                 \\
  vector<vector<type>> name(h, vector<type>(__VA_ARGS__))
#define VV(type, name, h, w)                                                   \\
  vector<vector<type>> name(h, vector<type>(w));                               \\
  in(name)
template <class T> auto min(const T &a) { return *min_element(all(a)); }
template <class T> auto max(const T &a) { return *max_element(all(a)); }
inline ll popcnt(ull a) { return __builtin_popcountll(a); }
ll gcd(ll a, ll b) {
  while (b) {
    ll c = b;
    b = a % b;
    a = c;
  }
  return a;
}
ll lcm(ll a, ll b) {
  unless(a && b) return 0;
  return a * b / gcd(a, b);
}
ll intpow(ll a, ll b) {
  ll ans = 1;
  while (b) {
    if (b & 1)
      ans *= a;
    a *= a;
    b /= 2;
  }
  return ans;
}
ll modpow(ll a, ll b, ll p = mod) {
  ll ans = 1;
  while (b) {
    if (b & 1)
      (ans *= a) %= p;
    (a *= a) %= p;
    b /= 2;
  }
  return ans;
}
template <class T, class U> bool chmin(T &a, const U &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T, class U> bool chmax(T &a, const U &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
vector<ll> iota(ll n) {
  vector<ll> a(n);
  iota(all(a), 0);
  return a;
}
vector<pll> factor(ull x) {
  vector<pll> ans;
  for (ull i = 2; i * i <= x; i++)
    if (x % i == 0) {
      ans.push_back({i, 1});
      while ((x /= i) % i == 0)
        ans.back().second++;
    }
  if (x != 1)
    ans.push_back({x, 1});
  return ans;
}
map<ll, ll> factor_map(ull x) {
  map<ll, ll> ans;
  for (ull i = 2; i * i <= x; i++)
    if (x % i == 0) {
      ans[i] = 1;
      while ((x /= i) % i == 0)
        ans[i]++;
    }
  if (x != 1)
    ans[x] = 1;
  return ans;
}
vector<ll> divisor(ull x) {
  vector<ll> ans;
  for (ull i = 2; i * i <= x; i++)
    if (x % i == 0)
      ans.push_back(i);
  rrep(ans.size() - (ans.back() * ans.back() == x)) ans.push_back(x / ans[i]);
  return ans;
}
int scan() { return getchar(); }
void scan(int &a) { scanf("%d", &a); }
void scan(unsigned &a) { scanf("%u", &a); }
void scan(long &a) { scanf("%ld", &a); }
void scan(long long &a) { scanf("%lld", &a); }
void scan(char &a) {
  do {
    a = getchar();
  } while (a == ' ' || a == '\\n');
}
void scan(float &a) { scanf("%f", &a); }
void scan(double &a) { scanf("%lf", &a); }
void scan(long double &a) { scanf("%Lf", &a); }
void scan(string &a) { cin >> a; }
template <class T> void scan(vector<T> &a) {
  for (auto &&i : a)
    scan(i);
}
template <class T, size_t size> void scan(array<T, size> &a) {
  for (auto &&i : a)
    scan(i);
}
template <class T, class L> void scan(pair<T, L> &p) {
  scan(p.first);
  scan(p.second);
}
template <class T, size_t size> void scan(T (&a)[size]) {
  for (auto &&i : a)
    scan(i);
}
void in() {}
template <class Head, class... Tail> void in(Head &head, Tail &...tail) {
  scan(head);
  in(tail...);
}
void print() { putchar(' '); }
void print(bool a) { printf("%d", a); }
void print(int a) { printf("%d", a); }
void print(unsigned a) { printf("%u", a); }
void print(long a) { printf("%ld", a); }
void print(unsigned long long a) { printf("%llu", a); }
void print(char a) { printf("%c", a); }
void print(double a) { printf("%.15f", a); }
void print(long double a) { printf("%.15Lf", a); }
void print(const string &a) {
  for (auto &&i : a)
    print(i);
}
template <class T> void print(const vector<T> &a) {
  if (a.empty())
    return;
  print(a[0]);
  for (auto i = a.begin(); ++i != a.end();) {
    putchar(' ');
    print(*i);
  }
}
template <class T> void print(const deque<T> &a) {
  if (a.empty())
    return;
  print(a[0]);
  for (auto i = a.begin(); ++i != a.end();) {
    putchar(' ');
    print(*i);
  }
}
template <class T, size_t size> void print(const T (&a)[size]) {
  print(a[0]);
  for (auto i = a; ++i != end(a);) {
    putchar(' ');
    print(*i);
  }
}
template <class T> void print(const T &a) { cout << a; }
int out() {
  putchar('\\n');
  return 0;
}
template <class T> int out(const T &t) {
  print(t);
  putchar('\\n');
  return 0;
}
template <class Head, class... Tail>
int out(const Head &head, const Tail &...tail) {
  print(head);
  putchar(' ');
  out(tail...);
  return 0;
}
int first(bool i) { return out(i ? "first" : "second"); }
int yes(bool i) { return out(i ? "yes" : "no"); }
int Yes(bool i) { return out(i ? "Yes" : "No"); }
int YES(bool i) { return out(i ? "YES" : "NO"); }
int possible(bool i) { return out(i ? "possible" : "impossible"); }
int Possible(bool i) { return out(i ? "Possible" : "Impossible"); }
int POSSIBLE(bool i) { return out(i ? "POSSIBLE" : "IMPOSSIBLE"); }

using Graph = vector<vector<int>>;
using Graphw = vector<vector<pair<ll, ll>>>;
using mat = vector<vector<ll>>;
using vec = vector<ll>;

/*
namespace mp = boost::multiprecision;
// 任意長整数型
using Bint = mp::cpp_int;
// 仮数部長が32の浮動小数点数型
using Real32 = mp::number<mp::cpp_dec_float<32>>;
// 仮数部長が1024の浮動小数点数型
using Real1024 = mp::number<mp::cpp_dec_float<1024>>;
// 有理数型
using Rat = boost::rational<Bint>;
*/

/* 4 方向への隣接頂点への移動を表すベクトル */

signed main() {

  INT(N);
  ll A[N + 1];
  rep3(i, N) cin >> A[i];
  map<ll, ll> m;
  ll ans = 0;
  rep3(i, N) {
    ans += m[i - A[i]];
    m[A[i] + i]++;
  }
  out(ans);
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>

using namespace std;
#define _GLIBCXX_DEBUG
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
using ll = long long;
#define rep2(i, s, n) for (int i = (s); i < (int)(n); i++)
#define rep3(i, n) for (int i = 1; i < (int)(n + 1); i++)
#define rep4(i, s, n) for (int i = (s); i < (int)(n + 1); i++)
#define stlen(s) ll s.size() - 1
#define all(v) v.begin(), v.end()
int main() {
  const ll INF = 100100100100100100;

  int N, count = 0, count_R = 1;
  cin >> N;
  vector<ll> A(N + 1);
  vector<ll> L(N + 1);
  vector<ll> R(N + 1);
  rep3(i, N) {
    cin >> A[i];
    L[i] = i - A[i];
    R[i] = A[i] + i;
  }
  sort(all(L));
  sort(all(R));
  rep3(i, N) {
    rep4(j, count_R, N) {
      if (i == j) {
        break;
      } else if (R[j] > L[i]) {
        break;

      } else if (R[j] == L[i]) {
        count++;
      } else if (R[j] < L[i]) {
        count_R++;
      }
    }
    if (count_R > N) {
      break;
    }
  }
  cout << count << endl;
}