Submission #1092023

#	Time	Username	Problem	Language	Result	Execution time	Memory
1092023		underwaterkillerwhale	Mountains (NOI20_mountains)	C++17	100 / 100	72 ms	14164 KiB

Mountains

#include <bits/stdc++.h>
#define ll              long long
#define pii             pair<int,int>
#define pll             pair<ll,ll>
#define rep(i,m,n)      for(int i=(m); i<=(n); i++)
#define reb(i,m,n)      for(int i=(m); i>=(n); i--)
#define iter(id, v)     for(auto id : v)
#define fs              first
#define se              second
#define MP              make_pair
#define pb              push_back
#define bit(msk, i)     ((msk >> i) & 1)
#define SZ(v)           (ll)v.size()
#define ALL(v)          v.begin(),v.end()

using namespace std;

mt19937_64 rd(chrono :: steady_clock :: now ().time_since_epoch().count());
ll Rand (ll l, ll r) { return uniform_int_distribution<ll> (l, r) (rd); }

const int N = 3e5 + 2;
const int Mod = 1e9 + 7;
const ll INF = 1e16;
const ll BASE = 137;
const int szBL = 350;

struct fenwick_Tree {
    int m;
    int fen[N];

    void init (int n) {
        m = n;
    }
    void update (int pos, int val) {
        for (; pos <= m; pos += pos & -pos) fen[pos] += val;
    }

    int get (int pos) {
        int res = 0;
        for (;pos > 0; pos -= pos & -pos) res += fen[pos];
        return res;
    }
    int get (int u, int v) {
        if (u > v) return 0;
        return get(v) - get(u - 1);
    }
}BIT;

int n;
ll a[N];
pll b[N];

void solution () {
    cin >> n;
    rep (i, 1, n) cin >> a[i];
    BIT.init(n);
    rep (i, 1, n) b[i] = MP(a[i], i);
    sort (b + 1, b + 1 + n);
    ll res = 0;
    rep (i, 1, n) {
        int L = i, R = i;
        while (R < n && b[R].fs == b[R + 1].fs) ++R;
        rep (j, L, R) {
            int val, pos;
            tie(val, pos) = b[j];
            res += 1LL * BIT.get(1, pos - 1) * BIT.get(pos + 1, n);
        }
        rep (j, L, R) {
            int val, pos;
            tie(val, pos) = b[j];
            BIT.update(pos, 1);
        }
        i = R;
    }
    cout << res <<"\n";

}

#define file(name) freopen(name".inp","r",stdin); \
freopen(name".out","w",stdout);
int main () {
//    file("DTREE");
    ios_base :: sync_with_stdio(false); cin.tie(0); cout.tie(0);
    int num_Test = 1;
//    cin >> num_Test;
    while (num_Test--)
        solution();
}
/*
no bug +5
*/

• 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