Submission #946773

#	Time	Username	Problem	Language	Result	Execution time	Memory
946773		GrindMachine	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	28 ms	5340 KiB

fancyfence

#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) (int)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

/*



*/

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

void solve(int test_case)
{
    ll n; cin >> n;
    vector<pll> a(n+5);
    rep1(i,n) cin >> a[i].ff;
    rep1(i,n) cin >> a[i].ss;

    vector<ll> p(n+5);
    rep1(i,n+1) p[i] = p[i-1]+a[i].ss;

    ll inv2 = (MOD+1)/2;

    auto ap_sum = [&](ll l, ll r){
        l %= MOD, r %= MOD;
        ll res = r*(r+1)-l*(l-1);
        res = (res%MOD+MOD)%MOD;
        res = res*inv2%MOD;
        return res;
    };

    ll s = 0;
    rep1(i,n) s += a[i].ss;

    // intra block
    ll ans = 0;
    rep1(i,n){
        auto [h,w] = a[i];
        ans += ap_sum(0,h)*ap_sum(0,w);
        ans %= MOD;
    }

    // inter block
    auto f = [&](ll l, ll r){
        ll wsum = (p[r]-p[l-1])%MOD;
        ll hways = ap_sum(0,a[l].ff);
        return wsum*hways%MOD;
    };

    vector<ll> stk;
    ll sum = 0;
    stk.pb(n+1);

    rev(i,n,1){
        auto [h,w] = a[i];
        while(h <= a[stk.back()].ff){
            ll siz = sz(stk);
            sum -= f(stk[siz-1],stk[siz-2]-1);
            sum = (sum%MOD+MOD)%MOD;
            stk.pop_back();
        }

        ll add = sum;

        {
            ll l = i+1, r = stk.back()-1;
            ll wsum = (p[r]-p[l-1])%MOD;
            ll hways = ap_sum(0,h);
            add = (add+wsum*hways)%MOD;
        }

        ans = (ans+add*w)%MOD;
        
        sum = (sum+f(i,stk.back()-1))%MOD;
        stk.pb(i);
    }

    cout << ans << endl;
}

int main()
{
    fastio;

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

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

    return 0;
}

• Subtask 1: 0 / 0
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 15 / 15
• Subtask 5: 15 / 15
• Subtask 6: 18 / 18
• Subtask 7: 27 / 27