Submission #945602

#	Time	Username	Problem	Language	Result	Execution time	Memory
945602		siewjh	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	20 ms	6352 KiB

fancyfence

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll mod = 1e9 + 7;
ll nc2(ll x){
	return x * (x - 1) / 2 % mod;
}
int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(0); cout.tie(0);
	int nums; cin >> nums;
	vector<ll> wv(nums), hv(nums);
	for (int i = 0; i < nums; i++) cin >> hv[i];
	for (int i = 0; i < nums; i++) cin >> wv[i];
	vector<tuple<ll, ll, ll>> st;
	ll ans = 0, sum = 0;
	for (int i = 0; i < nums; i++){
		ans = (ans + nc2(hv[i] + 1) * nc2(wv[i] + 1) % mod) % mod;
		ll wk = 0;
		while (!st.empty() && get<0>(st.back()) >= hv[i]){
			ll h, w, val; tie(h, w, val) = st.back();
			wk = (wk + w) % mod; sum = (sum - val + mod) % mod;
			st.pop_back();
		}
		ans = (ans + wk * nc2(hv[i] + 1) % mod * wv[i] % mod) % mod;
		ans = (ans + sum * wv[i] % mod) % mod;
		wk = (wk + wv[i]) % mod;
		ll nval = wk * nc2(hv[i] + 1) % mod;
		sum = (sum + nval) % mod;
		st.push_back({hv[i], wk, nval});
	}
	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