Submission #570148

#	Time	Username	Problem	Language	Result	Execution time	Memory
570148		HunterXD	Mountains (NOI20_mountains)	C++17	100 / 100	469 ms	33244 KiB

Mountains

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> ii;
typedef vector <int> vi;
typedef vector <ll> vl;
typedef vector<string> vs;
typedef vector<bool> vb;
typedef vector <char> vc;
typedef vector<ii> vii;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef vector<vc> vvc;
typedef vector<vs> vvs;
typedef pair<ll,ll> pl;
typedef double dou;
typedef vector<pl> vpl;
typedef unsigned long long ull;
typedef uint64_t i64;
typedef vector<ull> vull;

#define f first 
#define s second 
#define pb push_back 
#define sz(x) int((x).size())
#define all(x) begin(x), end(x)
#define ts to_string
#define lb lower_bound 
#define ub upper_bound
#define yes cout<<'Y'<<'E'<<'S'<<endl
#define no cout<<'N'<<'O'<<endl
#define nd "\n"

void setIO(string name=""){ios_base::sync_with_stdio(0);cin.tie(0);if(sz(name)){freopen((name+".in").c_str(),"r",stdin);freopen((name+".out").c_str(),"w",stdout);}}
 
ll gcd(ll a, ll b) {return b == 0 ? a : gcd(b, a % b);}
ll mcm(ll a, ll b) {return (a * b) / gcd(a, b);}
bool prime(ll n) {for(int i=2; i<=sqrt(n); i++) if(n%i==0) return false; return true;}
struct compii{bool operator()(const ii &a, const ii &b){if(a.f==a.s)return a.s<b.s;return a.f>b.f;}};
bool comp(int a, int b) {return a>b;}
ll binpow(ll n, ll x){ll ans=1; while(x){if(x&1){ans*=n;}n*=n; x>>=1;} return ans;}

namespace operators {
template<typename T1, typename T2>istream& operator>>(istream& in, pair<T1, T2>& x){in >> x.first >> x.second;return in;}
template<typename T1, typename T2>ostream& operator<<(ostream& out, pair<T1, T2> x){out << x.first << " " << x.second;return out;}
template<typename T1>istream& operator>>(istream& in, vector<T1>& x) {for (auto& i : x) in >> i;return in;}
template<typename T1>ostream& operator<<(ostream& out, vector<T1>& x) {for (auto& i : x) out << i << " ";return out;}
template<typename T1, typename T2>ostream& operator<<(ostream& out, vector<pair <T1,T2>>& x) {for (auto& i : x) out << i.f << " "<<i.s;return out;}
template<typename T1, typename T2>istream& operator>>(istream& in, vector<pair <T1,T2>>& x) {for (auto& i : x) in >> i.f >>i.s;return in;}
}

using namespace operators;

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

const int pmod = 998244353;
const int mod = 1e9+7;
const ll inf=1e18;

ll sum(ll a, ll b){
  return (( (a+mod) %mod) + ((b+mod)%mod))%mod;
}

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

///

struct FT{
  vector<ll> ft;
  ll n;

  FT(ll m){
    n = m;
    ft.assign(n+1, 0);
  }

  ll lsb(ll i){
    return (i)&(-i);
  }

  void add(ll i, ll k){
    while(i <= n){
      ft[i]+= k;
      i+= lsb(i);
    }
  }

  ll get(ll r){
    ll res = 0;
    while(r){
      res+= ft[r];
      r-= lsb(r);
    }
    return res;
  }

  ll range(ll i, ll j){
    if(i == 0) return get(j);
    return get(j) - get(i-1);
  }
};

void solve(){
  ll n; 
  cin >> n;

  vector<ll> a(n, 0), b;
  for(ll i = 0; i < n; i++){
    cin >> a[i];
  }

  b = a;
  sort(all(b));
  map<ll,ll> compress;

  ll next = 1;
  for(auto v: b){
    if(!compress[v]){
      compress[v] = next++;
    }
  }

  for(ll i = 0; i < n; i++){
    a[i] = compress[a[i]];
  }

  FT left(n), right(n);
  ll l[n], r[n];
  
  for(ll i = 0; i < n; i++){
    l[i] = left.range(1, a[i]-1);
    left.add(a[i], 1);
  }

  for(ll i = n-1; i >= 0; i--){
    r[i] = right.range(1, a[i]-1);
    right.add(a[i], 1);
  }

  ll res = 0; 

  for(ll i = 0; i < n; i++){
    res+= l[i]*r[i];
  }

  cout << res << endl;

}

int main (){
  setIO("");
  int t=1;
  //cin >> t;
  while(t-->0) solve();
  return 0;
}

Compilation message (stderr)

Mountains.cpp: In function 'void setIO(std::string)':
Mountains.cpp:34:88: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   34 | void setIO(string name=""){ios_base::sync_with_stdio(0);cin.tie(0);if(sz(name)){freopen((name+".in").c_str(),"r",stdin);freopen((name+".out").c_str(),"w",stdout);}}
      |                                                                                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Mountains.cpp:34:128: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   34 | void setIO(string name=""){ios_base::sync_with_stdio(0);cin.tie(0);if(sz(name)){freopen((name+".in").c_str(),"r",stdin);freopen((name+".out").c_str(),"w",stdout);}}
      |                                                                                                                         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 2 / 2
• Subtask 2: 4 / 4
• Subtask 3: 9 / 9
• Subtask 4: 36 / 36
• Subtask 5: 28 / 28
• Subtask 6: 9 / 9
• Subtask 7: 12 / 12