Problem p03498 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#include <iostream>

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep_r(i, n) for (int i = n - 1; i >= 0; i--)
#define rep1(i, n) for (int i = 1; i <= (int)(n); i++)
#define REP(i, n) for (int i = 0, i##_len = (n); i < i##_len; ++i)
#define all(x) (x).begin(), (x).end()
#define SZ(x) ((ll)(x).size())
#define bit(n) (1LL << (n))
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());

#define INF bit(60)
#define pb push_back
#define mod 1000000007

using namespace std;
using uif = uint_fast64_t;
using ll = long long int;
using tTree = __gnu_pbds::tree<ll, __gnu_pbds::null_type, less<ll>,
                               __gnu_pbds::rb_tree_tag,
                               __gnu_pbds::tree_order_statistics_node_update>;

ll dx[4] = {1, 0, -1, 0};
ll dy[4] = {0, 1, 0, -1};

#define FACSIZE 200002

ll invfac[FACSIZE];
ll fac[FACSIZE];

template <class T> bool chmax(T &, const T &);
template <class T> bool chmin(T &, const T &);
ll gcd(ll, ll);
ll powLL(ll x, ll y);

ll mod_pow(ll, ll);
ll mod_add(ll, ll);
ll mod_mul(ll, ll);
ll mod_div(ll, ll);
ll comb(ll, ll);
void make_fact(ll);
void make_invfact(ll);
void fact_init();

int main(void) {
  ll n;
  cin >> n;
  vector<ll> A(n);
  rep(i, n) cin >> A[i];
  using pa = pair<ll, ll>;
  pa AMax = make_pair(A[0], 0LL);
  pa AMin = make_pair(A[0], 0LL);

  for (ll i = 1; i < n; i++) {
    auto x = A[i];
    if (x > AMax.first) {
      AMax = make_pair(A[i], i);
    }
    if (x < AMin.first) {
      AMin = make_pair(A[i], i);
    }
  }

  queue<pa> que;

  if (abs(AMax.first >= abs(AMin.first))) {
    for (ll i = 0; i < n; i++) {
      if (i != AMax.second) {
        que.push(make_pair(AMax.second + 1, i + 1));
      }
    }
    for (ll i = 1; i < n; i++) {
      que.push(make_pair(i, i + 1));
    }
  } else {
    for (ll i = 0; i < n; i++) {
      if (i != AMin.second) {
        que.push(make_pair(AMin.second + 1, i + 1));
      }
    }
    for (ll i = n; i > 1; i++) {
      que.push(make_pair(i, i - 1));
    }
  }
  cout << que.size() << endl;
  while (!que.empty()) {
    auto q = que.front();
    que.pop();
    cout << q.first << " " << q.second << endl;
  }

  return 0;
}

ll mod_pow(ll x, ll r) {
  if (r == 0)
    return 1;
  else if (r == 1)
    return x % mod;
  else if (r % 2 == 0) {
    ll t = mod_pow(x, r / 2) % mod;
    return mod_mul(t, t);
  } else {
    ll t = mod_pow(x, r / 2) % mod;
    ll k = mod_mul(t, t);
    return (k % mod) * (x % mod);
  }
}
ll mod_add(ll a, ll b) { return ((a % mod) + (b % mod)) % mod; }

ll mod_mul(ll a, ll b) { return ((a % mod) * (b % mod)) % mod; }

ll mod_div(ll a, ll b) { return mod_mul(a, mod_pow(b, mod - 2)); }

void fact_init() {
  make_fact(FACSIZE - 1);
  make_invfact(FACSIZE);
}

void make_fact(ll n) {
  fac[0] = 1;
  rep(i, n) { fac[i + 1] = mod_mul(fac[i], i + 1); }
}

void make_invfact(ll n) {
  invfac[n] = mod_pow(fac[n], mod - 2);
  for (int i = n - 1; i >= 0; i--) {
    invfac[i] = mod_mul(invfac[i + 1], i + 1);
  }
}

ll comb(ll n, ll r) {

  return mod_mul(mod_mul(fac[n], invfac[r]), invfac[n - r]);
}
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;
}

ll qp(ll a, ll b) {
  ll ans = 1LL;
  do {
    if (b & 1LL)
      ans = 1LL * mod_mul(ans, a) % mod;
    a = 1LL * mod_mul(a, a) % mod;
  } while (b >>= 1LL);
  return ans;
}
ll qp(ll a, ll b, ll mo) {
  ll ans = 1LL;
  do {
    if (b & 1LL)
      ans = 1LL * (ans % mo) * (a % mo);
    a = 1LL * (a % mo) * (a % mo);
  } while (b >>= 1LL);
  return ans;
}
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll powLL(ll x, ll y) {
  ll ans = 1LL;
  for (ll i = 0LL; i < y; i++)
    ans *= x;
  return ans;
}

Fixed submission:
#include <bits/stdc++.h>
#include <iostream>

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep_r(i, n) for (int i = n - 1; i >= 0; i--)
#define rep1(i, n) for (int i = 1; i <= (int)(n); i++)
#define REP(i, n) for (int i = 0, i##_len = (n); i < i##_len; ++i)
#define all(x) (x).begin(), (x).end()
#define SZ(x) ((ll)(x).size())
#define bit(n) (1LL << (n))
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());

#define INF bit(60)
#define pb push_back
#define mod 1000000007

using namespace std;
using uif = uint_fast64_t;
using ll = long long int;
using tTree = __gnu_pbds::tree<ll, __gnu_pbds::null_type, less<ll>,
                               __gnu_pbds::rb_tree_tag,
                               __gnu_pbds::tree_order_statistics_node_update>;

ll dx[4] = {1, 0, -1, 0};
ll dy[4] = {0, 1, 0, -1};

#define FACSIZE 200002

ll invfac[FACSIZE];
ll fac[FACSIZE];

template <class T> bool chmax(T &, const T &);
template <class T> bool chmin(T &, const T &);
ll gcd(ll, ll);
ll powLL(ll x, ll y);

ll mod_pow(ll, ll);
ll mod_add(ll, ll);
ll mod_mul(ll, ll);
ll mod_div(ll, ll);
ll comb(ll, ll);
void make_fact(ll);
void make_invfact(ll);
void fact_init();

int main(void) {
  ll n;
  cin >> n;
  vector<ll> A(n);
  rep(i, n) cin >> A[i];
  using pa = pair<ll, ll>;
  pa AMax = make_pair(A[0], 0LL);
  pa AMin = make_pair(A[0], 0LL);

  for (ll i = 1; i < n; i++) {
    auto x = A[i];
    if (x > AMax.first) {
      AMax = make_pair(A[i], i);
    }
    if (x < AMin.first) {
      AMin = make_pair(A[i], i);
    }
  }

  queue<pa> que;

  if (abs(AMax.first >= abs(AMin.first))) {
    for (ll i = 0; i < n; i++) {
      if (i != AMax.second) {
        que.push(make_pair(AMax.second + 1, i + 1));
      }
    }
    for (ll i = 1; i < n; i++) {
      que.push(make_pair(i, i + 1));
    }
  } else {
    for (ll i = 0; i < n; i++) {
      if (i != AMin.second) {
        que.push(make_pair(AMin.second + 1, i + 1));
      }
    }
    for (ll i = n; i > 1; i--) {
      que.push(make_pair(i, i - 1));
    }
  }
  cout << que.size() << endl;
  while (!que.empty()) {
    auto q = que.front();
    que.pop();
    cout << q.first << " " << q.second << endl;
  }

  return 0;
}

ll mod_pow(ll x, ll r) {
  if (r == 0)
    return 1;
  else if (r == 1)
    return x % mod;
  else if (r % 2 == 0) {
    ll t = mod_pow(x, r / 2) % mod;
    return mod_mul(t, t);
  } else {
    ll t = mod_pow(x, r / 2) % mod;
    ll k = mod_mul(t, t);
    return (k % mod) * (x % mod);
  }
}
ll mod_add(ll a, ll b) { return ((a % mod) + (b % mod)) % mod; }

ll mod_mul(ll a, ll b) { return ((a % mod) * (b % mod)) % mod; }

ll mod_div(ll a, ll b) { return mod_mul(a, mod_pow(b, mod - 2)); }

void fact_init() {
  make_fact(FACSIZE - 1);
  make_invfact(FACSIZE);
}

void make_fact(ll n) {
  fac[0] = 1;
  rep(i, n) { fac[i + 1] = mod_mul(fac[i], i + 1); }
}

void make_invfact(ll n) {
  invfac[n] = mod_pow(fac[n], mod - 2);
  for (int i = n - 1; i >= 0; i--) {
    invfac[i] = mod_mul(invfac[i + 1], i + 1);
  }
}

ll comb(ll n, ll r) {

  return mod_mul(mod_mul(fac[n], invfac[r]), invfac[n - r]);
}
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;
}

ll qp(ll a, ll b) {
  ll ans = 1LL;
  do {
    if (b & 1LL)
      ans = 1LL * mod_mul(ans, a) % mod;
    a = 1LL * mod_mul(a, a) % mod;
  } while (b >>= 1LL);
  return ans;
}
ll qp(ll a, ll b, ll mo) {
  ll ans = 1LL;
  do {
    if (b & 1LL)
      ans = 1LL * (ans % mo) * (a % mo);
    a = 1LL * (a % mo) * (a % mo);
  } while (b >>= 1LL);
  return ans;
}
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll powLL(ll x, ll y) {
  ll ans = 1LL;
  for (ll i = 0LL; i < y; i++)
    ans *= x;
  return ans;
}