Submission #763693

#	Time	Username	Problem	Language	Result	Execution time	Memory
763693		GrindMachine	Žarulje (COI15_zarulje)	C++17	100 / 100	179 ms	25252 KiB

zarulje

// Om Namah Shivaya

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl

#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)

template<typename T>
void amin(T &a, T b) {
    a = min(a, b);
}

template<typename T>
void amax(T &a, T b) {
    a = max(a, b);
}

#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif

/*

refs:
edi
https://github.com/farmerboy95/CompetitiveProgramming/blob/92f327caaade93b9087bc969d8ed6fa4f596048c/COI/COI%2015-zarulje.cpp

*/

const int MOD = 1e9 + 7;
const int N = 2e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;

ll fact[N], ifact[N];

ll bexp(ll a, ll b) {
    a %= MOD;
    if (a == 0) return 0;

    ll res = 1;

    while (b) {
        if (b & 1) res = res * a % MOD;
        a = a * a % MOD;
        b >>= 1;
    }

    return res;
}

ll invmod(ll a) {
    return bexp(a, MOD - 2);
}

ll ncr(ll n, ll r) {
    if (n < 0 or r < 0 or n < r) return 0;
    return fact[n] * ifact[r] % MOD * ifact[n - r] % MOD;
}

ll npr(ll n, ll r) {
    if (n < 0 or r < 0 or n < r) return 0;
    return fact[n] * ifact[n - r] % MOD;
}

void precalc(ll n) {
    fact[0] = 1;
    rep1(i, n) fact[i] = fact[i - 1] * i % MOD;

    ifact[n] = invmod(fact[n]);
    rev(i, n - 1, 0) ifact[i] = ifact[i + 1] * (i + 1) % MOD;
}

void solve(int test_case)
{
    ll n,k; cin >> n >> k;
    precalc(n);

    vector<ll> a(n+5), b(k+5);
    rep1(i,n) cin >> a[i];
    rep1(i,k) cin >> b[i];

    vector<ll> ans(n+5);
    vector<pll> cnt(N);
    ll res = 1;

    auto upd = [&](ll i, ll j, ll c){
        auto &[x,y] = cnt[i];
        res = res * invmod(ncr(x+y,x)) % MOD;
        if(j == 1) x += c;
        else y += c;
        res = res * ncr(x+y,x) % MOD;
    };

    vector<ll> lx(n+5,1);
    stack<ll> st;

    rev(i,n,1){
        while(!st.empty() and a[i] < a[st.top()]){
            lx[st.top()] = i;
            st.pop();
        }
        st.push(i);
    }

    while(!st.empty()) st.pop();

    vector<ll> enter[n+5];
    rep1(i,n){
        enter[lx[i]].pb(i);
    }

    rep1(i,n){
        trav(j,enter[i]){
            upd(a[j],2,1);
        }
        upd(a[i],2,-1);

        ans[i] = res;

        while(!st.empty() and a[i] < a[st.top()]){
            upd(a[st.top()],1,-1);
            st.pop();
        }

        st.push(i);
        upd(a[i],1,1);
    }

    rep1(i,k){
        cout << ans[b[i]] << endl;
    }

    // rep1(ind,k){
    //     ll p = b[ind];
    //     ll mn = inf2;
    //     map<ll,pll> mp;

    //     for(int i = p+1; i <= n; ++i){
    //         if(a[i] > mn){
    //             // will def be removed without any option
    //             conts;
    //         }

    //         mn = a[i];
    //         mp[a[i]].ff++;
    //     }

    //     mn = inf2;
    //     rev(i,p-1,1){
    //         if(a[i] > mn){
    //             // will def be removed without any option
    //             conts;
    //         }

    //         mn = a[i];
    //         mp[a[i]].ss++;
    //     }

    //     ll ans = 1;
    //     for(auto [val,px] : mp){
    //         ll ways = ncr(px.ff+px.ss, px.ff);
    //         ans = ans * ways % MOD;
    //     }

    //     cout << ans << endl;
    // }
}

int main()
{
    fastio;

    int t = 1;
    // cin >> t;

    rep1(i, t) {
        solve(i);
    }

    return 0;
}

• Subtask 1: 22 / 22
• Subtask 2: 38 / 38
• Subtask 3: 40 / 40