Submission #1286945

#	Time	Username	Problem	Language	Result	Execution time	Memory
1286945		zyntherix	Fancy Fence (CEOI20_fancyfence)	C++20	30 / 100	17 ms	4700 KiB

fancyfence

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pi pair<int, int>
#define vi vector<int>
#define vs vector<string>
#define vb vector<bool>
#define vpi vector<pi>
#define pb push_back
#define all(a) (a).begin(), (a).end()
const int mod = 1e9 + 7;
int md_inv_2 = 500000004;

int sm(int x)
{
    return (((x * (x + 1)) % mod) * md_inv_2) % mod;
}

void solve()
{
    int n;
    cin >> n;
    int h[n], w[n];
    for (int i = 0; i < n; i++)
        cin >> h[i];
    int pref_w[n + 1];
    pref_w[0] = 0;
    for (int i = 0; i < n; i++)
    {
        cin >> w[i];
        pref_w[i + 1] = (pref_w[i] + w[i]) % mod;
    }
    vpi ns;
    vi nsi(n, n);
    ns.pb({0, n});
    for (int i = n - 1; i >= 0; i--)
    {
        while (ns.back().first >= h[i])
        {
            ns.pop_back();
        }
        nsi[i] = ns.back().second;
        ns.pb({h[i], i});
    }
    int ans = 0;
    vi st;
    st.pb(0);
    for (int i = 0; i < n; i++)
    {
        while (st.back() > h[i])
        {
            st.pop_back();
        }
        if (st.back() == h[i])
            continue;
        int w2 = (((pref_w[nsi[i]] - pref_w[i]) % mod) + mod) % mod;
        ans = (ans + (sm(w2) * (((sm(h[i]) - sm(st.back())) % mod) + mod) % mod) % mod) % mod;
        st.pb(h[i]);
    }
    cout << ans << '\n';
}

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(NULL);
    int t = 1;
    // cin >> t;
    while (t--)
    {
        solve();
    }
    return 0;
}

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