Submission #404745

#	Time	Username	Problem	Language	Result	Execution time	Memory
404745		SirCovidThe19th	Fancy Fence (CEOI20_fancyfence)	C++14	100 / 100	105 ms	6084 KiB

fancyfence

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

#define ll long long
#define mod (ll)1000000007

ll m(ll a, ll b){
    a %= mod; b %= mod;
    return (a*b)%mod;
}
ll m(ll a, ll b, ll c){
    a %= mod; b %= mod; c %= mod;
    return m(m(a, b), c);
}
ll sum(ll x){
    return ((x*(x+1))/2)%mod;
}

int main(){
    
    ll n, ans; cin >> n; 
    ll h[n+1], w[n+1], p[n+1], dp[n+1]; 
    h[0] = 0; p[0] = 0; dp[0] = 0, ans = 0;

    for (int i = 1; i <= n; i++) cin >> h[i];
    for (int i = 1; i <= n; i++) cin >> w[i];
    for (int i = 1; i <= n; i++) p[i] = p[i-1]+w[i];

    stack<ll> stk; stk.push(0);

    for (int i = 1; i <= n; i++){
        while (!stk.empty() and h[stk.top()] >= h[i]) stk.pop();
        dp[i] = dp[stk.top()] + m(sum(h[i]), (p[i]-p[stk.top()]));
        ans += m(dp[stk.top()], w[i]) + m(sum(h[i]), (p[i-1]-p[stk.top()]), w[i]) + m(sum(h[i]), sum(w[i]));
        dp[i] %= mod; ans %= mod; stk.push(i);
    }

    cout<<ans;
}

• 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