Submission #576725

#	Time	Username	Problem	Language	Result	Execution time	Memory
576725		timreizin	Fancy Fence (CEOI20_fancyfence)	C++17	12 / 100	1 ms	340 KiB

fancyfence

#include <iostream>
#include <vector>
#include <array>
#include <algorithm>
#include <iomanip>
#include <cmath>
#include <stack>
#include <numeric>

using namespace std;

using ll = long long;

const ll MOD = 1e9 + 7;

ll asum(ll n)
{
    return ((n * (n + 1)) / 2) % MOD;
}

int main()
{
    cin.tie(0)->sync_with_stdio(0);
    //freopen("/Users/timreizin/Downloads/sample/input1.txt", "r", stdin);
    int n;
    cin >> n;
    vector<ll> h(n), w(n);
    for (ll &i : h) cin >> i;
    for (ll &i : w) cin >> i;
    vector<ll> pref(n + 1);
    partial_sum(w.begin(), w.end(), pref.begin() + 1);
    vector<int> sl(n, -1), sr(n, n);
    stack<int> help;
    for (int i = 0; i < n; ++i)
    {
        while (!help.empty() && h[help.top()] >= h[i]) help.pop();
        if (!help.empty()) sl[i] = help.top();
        help.push(i);
    }
    while (!help.empty()) help.pop();
    for (int i = n - 1; i >= 0; --i)
    {
        while (!help.empty() && h[help.top()] > h[i]) help.pop();
        if (!help.empty()) sr[i] = help.top();
        help.push(i);
    }
    ll res = 0;
    for (int i = 0; i < n; ++i)
    {
        if (i + 1 < n)
        {
            ll sum = w[i] * w[i + 1] % MOD - 1;
            if (sum < 0) sum += MOD;
            res = (res + sum * min(h[i], h[i + 1])) % MOD;
        }
        res = (res + asum(h[i]) * asum(w[i])) % MOD;
        ll l1 = (pref[i] - pref[sl[i] + 1]) % MOD;
        ll l2 = (pref[sr[i]] - pref[i + 1]) % MOD;
        ll sum = (l1 + 1) * (l2 + 1) % MOD - 1;
        if (sum < 0) sum += MOD;
        res = (res + sum * asum(h[i])) % MOD;
    }
    cout << res;
    return 0;
}
/*
2
2 2
2 2
*/

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