Submission #868583

#	Time	Username	Problem	Language	Result	Execution time	Memory
868583		mariaclara	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	24 ms	6836 KiB

fancyfence

#pragma GCC optimize "Ofast"
#include <bits/stdc++.h>

using namespace std;

typedef long long int ll;
typedef tuple<ll,ll,ll> trio;
typedef pair<int,int> pii;
const int MAXN = 1e5+10;
const ll MOD = 1e9+7;
#define all(x) x.begin(), x.end()
#define mk make_pair
#define pb push_back
#define f first
#define s second

ll n, resp, h[MAXN], w[MAXN], ant[MAXN], pos[MAXN], pw[MAXN];
int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    
    cin >> n;

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

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

    stack<int> val;
    val.push(0);
    for(int i = 1; i <= n; i++) {
        while(h[val.top()] > h[i]) val.pop();
        ant[i] = val.top();
        val.push(i);
    }
    while(!val.empty()) val.pop();
    val.push(n+1);

    for(int i = n; i >= 1; i--) {
        while(h[val.top()] >= h[i]) val.pop();
        pos[i] = val.top();
        val.push(i);
    }

    for(int i = 1; i <= n; i++) {
        ll l = ant[i]+1, r = pos[i]-1;
        ll tot = (((pw[r]-pw[l-1]+1)%MOD) * ((pw[r]-pw[l-1])%MOD))/2;
        ll casoA = (((pw[r]-pw[i]+1)%MOD) * ((pw[r]-pw[i])%MOD))/2;
        ll casoB = (((pw[i-1]-pw[l-1]+1)%MOD) * ((pw[i-1]-pw[l-1])%MOD))/2;
        resp +=  ((tot%MOD - casoA%MOD - casoB%MOD)%MOD) * ((h[i] * (h[i]+1) / 2)%MOD);
        resp %= MOD;
    }

    cout << (resp + MOD) % MOD;
}
// g++ -std=c++17 clara.cpp -o clara

• 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