Submission #798244

#	Time	Username	Problem	Language	Result	Execution time	Memory
798244		vjudge1	Cryptography (NOI20_crypto)	C++17	100 / 100	360 ms	39644 KiB

Crypto

#include <bits/stdc++.h>
using namespace std;
#define futaba ios_base::sync_with_stdio(false); cin.tie(NULL);
#define rio return 0;
#define ll long long

const ll mod = 1e9 + 7;

// Fun things are fun. //

ll a[300005], b[300005], fac[300005], seg[1200005];

ll merge(ll a, ll b) {
    return a + b;
}

void build(int l, int r, int v) {
    if(l == r) seg[v] = 1;
    else {
        int mid = l + (r - l) / 2;
        build(l, mid, 2 * v);
        build(mid + 1, r, (2 * v) + 1);
        seg[v] = merge(seg[2 * v], seg[(2 * v) + 1]);
    }
}

void update(int l, int r, int v, int pos) {
    if(l == r) seg[v] = 0;
    else {
        int mid = l + (r - l) / 2;
        if(pos <= mid) update(l, mid, 2 * v, pos);
        else update(mid + 1, r, (2 * v) + 1, pos);
        seg[v]--; 
    }
}

ll query(int l, int r, int v, int lq, int rq) {
    if(lq <= l and r <= rq) return seg[v];
    if(lq > r or rq < l) return 0;
    int mid = l + (r - l) / 2;
    return merge(query(l, mid, 2 * v, lq, rq), query(mid + 1, r, (2 * v) + 1, lq, rq));
}

int main() {
    /* freopen(".txt", "r", stdin);
    freopen(".txt", "w", stdout); */
    futaba
    int n;
    cin >> n;
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
        b[i] = a[i];
    }
    sort(b + 1, b + n + 1);
    map<ll, int> mp;
    for(int i = 1; i <= n; i++) mp[b[i]] = i;
    vector<ll> v(n + 1);
    for(int i = 1; i <= n; i++) v[i] = mp[a[i]];
    fac[0] = 1;
    for(int i = 1; i <= n; i++) fac[i] = (fac[i - 1] * i) % mod;
    build(1, n, 1);
    ll ans = 1;
    for(int i = 1; i <= n; i++) {
        ans += fac[n - i] * query(1, n, 1, 1, v[i] - 1);
        ans %= mod;
        update(1, n, 1, v[i]);
    }
    if(ans < 0) ans += mod;
    cout << ans << '\n';
    rio
}

• Subtask 1: 5 / 5
• Subtask 2: 9 / 9
• Subtask 3: 10 / 10
• Subtask 4: 11 / 11
• Subtask 5: 21 / 21
• Subtask 6: 13 / 13
• Subtask 7: 19 / 19
• Subtask 8: 12 / 12