Submission #1043594

#	Time	Username	Problem	Language	Result	Execution time	Memory
1043594		Whisper	Mountains (NOI20_mountains)	C++17	100 / 100	161 ms	21724 KiB

Mountains

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

#define int long long
#define FOR(i, a, b) for (int i = a; i <= b; i++)
#define FORD(i, a, b) for (int i = b; i >= a; i --)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define REPD(i, n) for (int i = n - 1; i >= 0; --i)

#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)

constexpr ll LINF = (1ll << 60);
constexpr int INF = (1ll << 30);
constexpr int Mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

void setupIO(){
    #define name "Whisper"
    //Phu Trong from Nguyen Tat Thanh High School for gifted student
    srand(time(NULL));
    cin.tie(nullptr)->sync_with_stdio(false); cout.tie(nullptr);
    //freopen(name".inp", "r", stdin);
    //freopen(name".out", "w", stdout);
    cout << fixed << setprecision(10);
}

template <class X, class Y>
    bool minimize(X &x, const Y &y){
        X eps = 1e-9;
        if (x > y + eps) {x = y; return 1;}
        return 0;
    }

template <class X, class Y>
    bool maximize(X &x, const Y &y){
        X eps = 1e-9;
        if (x + eps < y) {x = y; return 1;}
        return 0;
    }

const int MAX = 3e5 + 5;
int nArr;
int a[MAX];

struct SegmentTree{
    int n;
    vector<int> f;
    SegmentTree(int _n = 0){
        this -> n = _n;
        f.resize((n << 1));
    }
    void modify(int p, int val){
        for (f[p += n] += val; p > 0; p >>= 1){
            f[p >> 1] = f[p] + f[p ^ 1];
        }
    }
    int query(int l, int r){
        int ans = 0;
        for(l += n, r += n + 1; l < r; l >>= 1, r >>= 1){
            if(l & 1) ans += f[l++];
            if(r & 1) ans += f[--r];
        }
        return ans;
    }
}l, r;
void Whisper(){
    cin >> nArr;
    for (int i = 1; i <= nArr; ++i) cin >> a[i];
    vector<int> compress;
    for (int i = 1; i <= nArr; ++i){
        compress.push_back(a[i]);
    }

    sort(compress.begin(), compress.end());
    compress.resize(unique(compress.begin(), compress.end()) - compress.begin());
    for (int i = 1; i <= nArr; ++i){
        a[i] = lower_bound(compress.begin(), compress.end(), a[i]) - compress.begin() + 1;
    }

    l = SegmentTree(nArr + 1), r = SegmentTree(nArr + 1);
    for (int i = 1; i <= nArr; ++i){
        r.modify(a[i], 1);
    }
    int ans = 0;
    for (int i = 1; i <= nArr; ++i){
        r.modify(a[i], -1);
        int left = l.query(1, a[i] - 1);
        int right = r.query(1, a[i] - 1);
        ans += left * right;
        l.modify(a[i], 1);
    }
    cout << ans;
}


signed main(){
    setupIO();
    int Test = 1;
//    cin >> Test;
    for ( int i = 1 ; i <= Test ; i++ ){
        Whisper();
        if (i < Test) cout << '\n';
    }
}

• 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