Submission #570241

#	Time	Username	Problem	Language	Result	Execution time	Memory
570241		Joshi503	Mountains (NOI20_mountains)	C++17	15 / 100	213 ms	262144 KiB

Mountains

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

using ll = long long;
using db = long double;
using str = string;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
using pd = pair<db, db>;
#define f first
#define s second

#define tcT template<class T
#define tcTU tcT, class U
tcT> using V = vector<T>;
tcT, size_t SZ > using AR = array<T, SZ>;
using vi = V<int>;
using vb = V<bool>;
using vl = V<ll>;
using vd = V<db>;
using vs = V<str>;
using vpi = V<pi>;
using vpl = V<pl>;

#define sz(x) int((x).size())
#define bg(x) begin(x)
#define all(x) bg(x), end(x)
#define rall(x) x.rbegin(), x.rend() 
#define sor(x) sort(all(x)) 
#define pb push_back

#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = ((b)-1); i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define rep(a) F0R(_,a)
#define each(a,x) for (auto& a: x)

const ll MOD = 1e9 + 7;
const ll MX = 1e9;
const ll INF = 1e18;
const db PI = acos((db)-1);
const int ddef[4]{ 1,0,-1,0 }, dataq[4]{ 0,1,0,-1 };
mt19937 rng((uint32_t)chrono::steady_clock::now().time_since_epoch().count());
template<class T> using pqg = priority_queue<T, vector<T>, greater<T>>;

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);
    }
}

void _print(char i) { cerr << i; }
void _print(string i) { cerr << i; }
void _print(float i) { cerr << i; }
void _print(int i) { cerr << i; }
void _print(double i) { cerr << i; }
void _print() { cerr << "\n"; };
template<typename x, typename y> void _print(pair<x, y>& t) { cerr << "{";_print(t.first);cerr << ", ";_print(t.second);cerr << "},"; }
template<typename x> void _print(x& t) { cerr << "{"; for (int i = 0;i < (int)t.size();i++) { _print(t[i]); if (i < (int)t.size() - 1) cerr << ", "; } cerr << "}"; }
template<typename x, typename... y> void _print(x a, y... b) { _print(a);if (sizeof...(b)) cerr << ", ";_print(b...); }
#define dbg(x...) cerr<<"["<<#x<<"] = [";_print(x);cerr<<"]\n";

int test;

void solve() {

    ll n; cin >> n;

    vi a(n);
    each(x, a) cin >> x;
    vi b = a;
    sor(b);
    if(a == b){
        cout << "0\n";
        return;
    }
    if(n <= 10000){
        ll ans = 0;
        FOR(i, 1, n - 1){
            ll cnt1 = 0, cnt2 = 0;
            for(ll j = 0; j < i; j++){
                cnt1 += (a[i] > a[j]);
            }
            for(ll j = i + 1; j < n; j++){
                cnt2 += (a[i] > a[j]);
            }
            ans += cnt1 * cnt2;
        }
        cout << ans << "\n";
        return;
    }
    map<ll, ll> m;
    ll cnt = 0;
    F0R(i, n){
        if(!m[b[i]]){
            m[b[i]] = cnt++;
        }
    }
    ll pref[n + 1][cnt];
    F0R(i, n){
        a[i] = m[a[i]];
    }
    F0R(i, n + 1){
        F0R(j, cnt){
            pref[i][j] = 0;
        }
    }
    for(ll i = 0; i < n; i++){
        for(ll j = 0; j < cnt; j++){
            pref[i + 1][j] = pref[i][j] + (j > a[i]);
        }
    }
    ll ans = 0;
    FOR(i, 1, n - 1){
        // cout << pref[i][a[i]] - pref[i - 1][a[i]] << " " << pref[n][a[i]] - pref[i][a[i]] << "\n";
        ans += (pref[i][a[i]]) * (pref[n][a[i]] - pref[i + 1][a[i]]);
    }
    for(ll j = 0; j < cnt; j++){
        for(ll i = 0; i < n + 1; i++){
        }
    } 

    cout << ans << "\n";
 
}

int main() {
    setIO("");
    int T = 1;
    // cin >> T;
    for (test = 1; test <= T; test++) solve();
    return 0;
}

Compilation message (stderr)

Mountains.cpp: In function 'void setIO(std::string)':
Mountains.cpp:50:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |         freopen((name + ".in").c_str(), "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Mountains.cpp:51:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |         freopen((name + ".out").c_str(), "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 2 / 2
• Subtask 2: 4 / 4
• Subtask 3: 9 / 9
• Subtask 4: 0 / 36
• Subtask 5: 0 / 28
• Subtask 6: 0 / 9
• Subtask 7: 0 / 12