Submission #759008

#	Time	Username	Problem	Language	Result	Execution time	Memory
759008		ymm	Fancy Fence (CEOI20_fancyfence)	C++17	12 / 100	1 ms	348 KiB

fancyfence

#include <bits/stdc++.h>
#define Loop(x,l,r) for (ll x = (l); x < (ll)(r); ++x)
#define LoopR(x,l,r) for (ll x = (r)-1; x >= (ll)(l); --x)
typedef long long ll;
typedef std::pair<int, int> pii;
typedef std::pair<ll , ll > pll;
using namespace std;

const int mod = 1e9+7;
const int N = 100'010;
int lft[N], rgt[N];
ll h[N], w[N], ps[N];
int n;

ll solve(int l, int r, int i, ll hx)
{
	if (l >= r)
		return 0;
	ll x = h[i] - hx;
	ll y = ps[r] - ps[l];
	ll ans = 0;
	ans += (x*(x+1)/2 % mod) * (y*(y+1)/2 % mod);
	ans += (x * hx % mod) * (y*(y+1)/2 % mod);
	ans += solve(l, i, lft[i], h[i]);
	ans += solve(i+1, r, rgt[i], h[i]);
	ans %= mod;
	return ans;
}

int main()
{
	cin.tie(0) -> sync_with_stdio(false);
	cin >> n;
	Loop (i,0,n)
		cin >> h[i];
	Loop (i,0,n) {
		cin >> w[i];
		ps[i+1] = ps[i] + w[i];
	}
	vector<int> vec;
	Loop (i,0,n) {
		int lst = -1;
		while (vec.size() && h[vec.back()] > h[i]) {
			lst = vec.back();
			vec.pop_back();
		}
		lft[i] = lst;
		if (vec.size())
			rgt[vec.back()] = i;
		vec.push_back(i);
	}
	cout << solve(0, n, vec[0], 0) << '\n';
}

• 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