Submission #1101190

#	Time	Username	Problem	Language	Result	Execution time	Memory
1101190		vladilius	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	39 ms	5248 KiB

fancyfence

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define pb push_back
#define ff first
#define ss second
const int mod = 1e9 + 7;

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    
    int n; cin>>n;
    vector<int> h(n + 1);
    for (int i = 1; i <= n; i++){
        cin>>h[i];
    }
    vector<int> w(n + 1);
    vector<ll> p(n + 1);
    for (int i = 1; i <= n; i++){
        cin>>w[i];
        p[i] = p[i - 1] + w[i];
    }
    
    auto sum = [&](int l, int r){
        return (p[r] - p[l - 1]) % mod;
    };
    
    ll out = 0;
    for (int i = 1; i <= n; i++){
        out += (((1LL * w[i] * (w[i] + 1) / 2) % mod) * ((1LL * h[i] * (h[i] + 1) / 2) % mod)) % mod;
    }
    
    vector<int> f(n + 1);
    vector<ll> pr(n + 1);
    function<void(int, int)> solve = [&](int l, int r){
        if (l == r) return;
        int m = (l + r) / 2;
        
        f[m] = h[m]; f[m + 1] = h[m + 1];
        for (int i = m - 1; i >= l; i--) f[i] = min(f[i + 1], h[i]);
        for (int i = m + 2; i <= r; i++) f[i] = min(f[i - 1], h[i]);
        
        pr[m] = 0;
        for (int i = m + 1; i <= r; i++){
            pr[i] = (pr[i - 1] + ((1LL * f[i] * (f[i] + 1) / 2) % mod * w[i]) % mod) % mod;
        }
        
        int j = m + 1;
        for (int i = m; i >= l; i--){
            while (j <= r && f[j] >= f[i]) j++;
            if (j <= r) out += (1LL * w[i] * (pr[r] - pr[j - 1])) % mod;
            if (m < j) out += (((1LL * f[i] * (f[i] + 1) / 2) % mod) * ((1LL * w[i] * sum(m + 1, j - 1)) % mod)) % mod;
        }
        out %= mod;
        
        solve(l, m); solve(m + 1, r);
    };
    solve(1, n);
    
    cout<<out<<"\n";
}

• 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