Problem p03987 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <bitset>
#include <complex>
#include <cstring>
#include <deque>
#include <iomanip>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <vector>

using namespace std;

typedef long long ll;
// typedef pair<int,int> Pint;
// typedef pair<ll, ll> P;
// typedef pair<ll, pair<ll, ll>> P;
// typedef tuple<int,int,int> T;
typedef vector<ll> vec;
typedef vector<vec> mat;
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define revrep(i, n) for (ll i = (n - 1); i >= 0; i--)
#define pb push_back
#define f first
#define s second
// const ll INFL = 1LL << 60;//10^18 = 2^60
const ll INFL = 1LL << 60;
const int INF = 1 << 30; // 10^9
ll MOD = 1e9 + 7;
// ll MOD  = 998244353;
vector<ll> dy = {0, 0, 1, -1, 1, 1, -1, -1, 0};
vector<ll> dx = {1, -1, 0, 0, 1, -1, 1, -1, 0};

ll max(ll a, ll b) { return (a > b) ? a : b; }
ll min(ll a, ll b) { return (a < b) ? a : b; }
ll pow_long(ll x, ll k) {
  ll res = 1;
  while (k > 0) {
    if (k % 2)
      res *= x;
    x *= x;
    k /= 2;
  }
  return res;
}
ll pow_mod(ll x, ll k) {
  x %= MOD;
  x += MOD;
  x %= MOD;
  ll res = 1;
  while (k > 0) {
    if (k % 2) {
      res *= x;
      res %= MOD;
    }
    x *= x;
    x %= MOD;
    k /= 2;
  }
  return res;
}
ll inverse(ll x) { return pow_mod(x, MOD - 2); };

// 最大公約数
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}

// 最小公倍数
ll lcm(ll x, ll y) { return x / gcd(x, y) * y; };

// コンビネーション
const int MAXcomb = 200010;
ll fac[MAXcomb], finv[MAXcomb], inv[MAXcomb];
// facはn!,finvは1/n!
// invは逆元
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAXcomb; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
ll comb(int n, int k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return fac[n] * finv[k] % MOD * finv[n - k] % MOD;
}

int main(void) {
  ll N;
  cin >> N;
  vector<ll> A(N), B(N);
  rep(i, N) {
    cin >> A[i];
    A[i]--;
    B[A[i]] = i;
  }
  ll ans = 0;
  set<ll> S;
  S.insert(-1);
  S.insert(N);
  rep(i, N) {
    ll pos = B[i];
    auto right = lower_bound(S.begin(), S.end(), pos);
    auto left = right;
    left--;
    ll l = *left;
    ll r = *right;
    ans += (i + 1) * (pos - l) * (r - pos);
    S.insert(pos);
  }
  cout << ans << endl;
}


Fixed submission:
#include <algorithm>
#include <bitset>
#include <complex>
#include <cstring>
#include <deque>
#include <iomanip>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <vector>

using namespace std;

typedef long long ll;
// typedef pair<int,int> Pint;
// typedef pair<ll, ll> P;
// typedef pair<ll, pair<ll, ll>> P;
// typedef tuple<int,int,int> T;
typedef vector<ll> vec;
typedef vector<vec> mat;
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define revrep(i, n) for (ll i = (n - 1); i >= 0; i--)
#define pb push_back
#define f first
#define s second
// const ll INFL = 1LL << 60;//10^18 = 2^60
const ll INFL = 1LL << 60;
const int INF = 1 << 30; // 10^9
ll MOD = 1e9 + 7;
// ll MOD  = 998244353;
vector<ll> dy = {0, 0, 1, -1, 1, 1, -1, -1, 0};
vector<ll> dx = {1, -1, 0, 0, 1, -1, 1, -1, 0};

ll max(ll a, ll b) { return (a > b) ? a : b; }
ll min(ll a, ll b) { return (a < b) ? a : b; }
ll pow_long(ll x, ll k) {
  ll res = 1;
  while (k > 0) {
    if (k % 2)
      res *= x;
    x *= x;
    k /= 2;
  }
  return res;
}
ll pow_mod(ll x, ll k) {
  x %= MOD;
  x += MOD;
  x %= MOD;
  ll res = 1;
  while (k > 0) {
    if (k % 2) {
      res *= x;
      res %= MOD;
    }
    x *= x;
    x %= MOD;
    k /= 2;
  }
  return res;
}
ll inverse(ll x) { return pow_mod(x, MOD - 2); };

// 最大公約数
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}

// 最小公倍数
ll lcm(ll x, ll y) { return x / gcd(x, y) * y; };

// コンビネーション
const int MAXcomb = 200010;
ll fac[MAXcomb], finv[MAXcomb], inv[MAXcomb];
// facはn!,finvは1/n!
// invは逆元
void COMinit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAXcomb; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
ll comb(int n, int k) {
  if (n < k)
    return 0;
  if (n < 0 || k < 0)
    return 0;
  return fac[n] * finv[k] % MOD * finv[n - k] % MOD;
}

int main(void) {
  ll N;
  cin >> N;
  vector<ll> A(N), B(N);
  rep(i, N) {
    cin >> A[i];
    A[i]--;
    B[A[i]] = i;
  }
  ll ans = 0;
  set<ll> S;
  S.insert(-1);
  S.insert(N);
  rep(i, N) {
    ll pos = B[i];
    auto right = S.lower_bound(pos);
    auto left = right;
    left--;
    ll l = *left;
    ll r = *right;
    ans += (i + 1) * (pos - l) * (r - pos);
    S.insert(pos);
  }
  cout << ans << endl;
}