Submission #856440

#	Time	Username	Problem	Language	Result	Execution time	Memory
856440		Niktop	Fancy Fence (CEOI20_fancyfence)	C++14	27 / 100	21 ms	3596 KiB

fancyfence

#include <bits/stdc++.h>
using namespace std;

#define int long long
#define pii pair<int,int>
#define mii map<int,int>
#define F first
#define S second
#define pb push_back
#define fast ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#pragma GCC optimize ("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize ("-O2")

const int N = 1e5+5, mod = 1e9+7;
int h[N], w[N], ans[N], ps[N];
vector <int> v;
int inv2;
int pw(int a, int b)
{
    if (b == 0)
        return 1;
    if (b % 2 == 1)
        return (pw(a * a % mod, b/2) % mod) * a % mod;
    return pw(a * a % mod, b/2) % mod;
}

int c2(int x)
{
    x %= mod;
    return (x * (x-1+mod) % mod) * inv2 % mod;
}

int tr(int hr, int wr)
{
    hr %= mod, wr %= mod;
    int a;
    a = (((c2(hr * wr % mod) + (hr * c2(wr))) % mod) +  (wr * c2(hr))) % mod;
    a = (a * inv2) % mod;
    return (a + (hr * wr%mod))%mod;
}
int32_t main()
{
    fast
    int n;
    cin >> n;
    inv2 = pw(2,mod-2);
    for (int i = 1; i <= n; i++)
        cin >> h[i];
    for (int i = 1; i <= n; i++)
        cin >> w[i], ps[i] = ps[i-1] + w[i], ps[i] %= mod;
    h[0] = 0;
    v.pb(0);
    int sum = 0;
    for (int i = 1; i <= n; i++)
    {
        while (h[v[v.size()-1]]>=h[i])
            v.pop_back();
        int j = v[v.size()-1];
        v.pb(i);
        int tw = (ps[i] - ps[j] + mod)%mod;
        ans[i] = (tr(tw,h[i]) - tr(tw-w[i]+mod,h[i])+mod);
        ans[i] %= mod;
        ans[i] += (w[i]*ans[j])%mod;
        ans[i] %= mod;
        sum += ans[i];
        sum %= mod;
    }
    cout << sum << endl;
}

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