Submission #709692

#	Time	Username	Problem	Language	Result	Execution time	Memory
709692		Spade1	Fancy Fence (CEOI20_fancyfence)	C++14	0 / 100	1 ms	340 KiB

fancyfence

#include<bits/stdc++.h>
//#include "grader.h"
#define pii pair<int, int>
#define pll pair<long long, long long>
#define ll long long
#define ld long double
#define st first
#define nd second
#define pb push_back
#define INF INT_MAX
using namespace std;

const int N = 1e5 + 10;
const int M = 1e9+7;
stack<int> s;

ll h[N], w[N], qs[N];

ll power(ll a, ll b) {
    if (b == 0) return 1;
    ll ret = power(a, b/2);
    if (b&1) return ret*ret%M*a%M;
    else return ret*ret%M;
}

void solve() {
    int n; cin >> n;
    for (int i = 1; i <= n; ++i) cin >> h[i];
    for (int i = 1; i <= n; ++i) cin >> w[i], qs[i] = qs[i-1]+w[i];

    ll ans = 0;
    ll inv = power(2, M-2);
    s.push(0);
    for (int i = 1; i <= n; ++i) {
        while (h[s.top()] > h[i]) {
            ll H = h[s.top()];
            H %= M;
            ll W = qs[i-1] - qs[s.top()-1];
            W %= M;
            s.pop();
            H -= max(h[s.top()], h[i]);
            ans += ((H)*(H+1)%M*inv%M * (W*(W+1)%M*inv)%M)%M;
            ans %= M;
            ans += (H*h[s.top()]%M * (W*(W+1)%M*inv)%M)%M;
            ans %= M;
        }
        s.push(i);
    }
    while (s.size() > 1) {
        ll H = h[s.top()];
        H %= M;
        ll W = qs[n] - qs[s.top()-1];
        W %= M;
        s.pop();
        H -= h[s.top()];
        ans += ((H)*(H+1)%M*inv%M * (W*(W+1)%M*inv)%M)%M;
        ans %= M;
        ans += (H*h[s.top()]%M * (W*(W+1)%M*inv)%M)%M;
        ans %= M;
    }
    cout << ans << '\n';
}

int main() {
    ios_base::sync_with_stdio(0); cin.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: 0 / 15
• Subtask 5: 0 / 15
• Subtask 6: 0 / 18
• Subtask 7: 0 / 27