Submission #1290199

#	Time	Username	Problem	Language	Result	Execution time	Memory
1290199		mingga	Fancy Fence (CEOI20_fancyfence)	C++20	100 / 100	19 ms	2928 KiB

fancyfence

#include "bits/stdc++.h"

using namespace std;

#define ln "\n"
#define pb push_back
#define fi first
#define se second
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define ll long long
const int mod = 1e9 + 7;
const int inf = 2e9;
const int div2 = 500000004;

const int N = 1e5 + 7;
int n, h[N], w[N], lef[N], rig[N], ps[N];

int add(int x, int y) {
	x += y;
	if(x >= mod) x -= mod;
	if(x < 0) x += mod;
	return x;
}

int mul(int x, int y) {
	return (1ll * x * y) % mod;
}

int get(int l, int r) {
	return add(ps[r], -ps[l - 1]);
}


signed main() {
    cin.tie(0) -> sync_with_stdio(0);
    #define task ""
    if(fopen(task ".INP", "r")) {
        freopen(task ".INP", "r", stdin);
        freopen(task ".OUT", "w", stdout);
    }
    cin >> n;
    for(int i = 1; i <= n; i++) cin >> h[i];
    for(int i = 1; i <= n; i++) cin >> w[i], ps[i] = add(ps[i - 1], w[i]);
    ps[n + 1] = ps[n];
    vector<int> st;
	h[0] = h[n + 1] = -inf;
	st.pb(0);
	for(int i = 1; i <= n; i++) {
		while(h[st.back()] >= h[i]) st.pop_back();
		lef[i] = st.back();
		st.pb(i);
	}
	st.clear();
	st.pb(n + 1);
	int ans = 0;
	for(int i = n; i > 0; i--) {
		while(h[st.back()] > h[i]) st.pop_back();
		rig[i] = st.back();
		st.pb(i);
		int tot = get(lef[i] + 1, rig[i] - 1);
		tot = mul(mul(tot, tot + 1), div2);
		int l = get(lef[i] + 1, i - 1);
		int r = get(i + 1, rig[i] - 1);
		l = mul(mul(l, l + 1), div2);
		r = mul(mul(r, r + 1), div2);
		int ext2 = mul(mul(h[i], h[i] + 1), div2);
		tot = add(tot, -l);
		tot = add(tot, -r);
		ans = add(ans, mul(ext2, tot));
	}
	cout << ans << ln;
    cerr << "\nTime: " << clock() * 1000 / CLOCKS_PER_SEC;
} 

Compilation message (stderr)

fancyfence.cpp: In function 'int main()':
fancyfence.cpp:39:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   39 |         freopen(task ".INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
fancyfence.cpp:40:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   40 |         freopen(task ".OUT", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• 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