Submission #674786

#	Time	Username	Problem	Language	Result	Execution time	Memory
674786		faribourz	Fancy Fence (CEOI20_fancyfence)	C++14	60 / 100	27 ms	5416 KiB

fancyfence

// Only GOD
// believe in yourself
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;

#define F first
#define S second
#define pb push_back
#define all(x) x.begin(), x.end()
#define bit(x, y) ((x >> y)&1)
#define sz(x) (int)x.size()
#define kill(x) return cout << x << '\n', void()
#define KILL(x) return cout << x << '\n', 0
#define int ll 
const int N = 2e5+10;
const int INF = 1e9;
const int MOD = 1e9+7;
int mul(int a, int b){
	a %= MOD;
	b %= MOD;
	return (a*b)%MOD;
}
int add(int a, int b){
	return (a+b+MOD)%MOD;
}
int dp[N], h[N], w[N], ps[N];
int inv;
int f(int n){
	return mul(mul(n, n+1)%MOD, inv)%MOD;
}
int pw(int a, int b){
	int res = 1;
	while(b){
		if(b & 1)
			res = mul(a, res);
		a = mul(a, a);
		b >>= 1;
	}
	return res;
}
int32_t main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	int n;
	cin >> n;
	inv = pw(2, MOD-2);
	bool fe = 1;
	for(int i = 1; i <= n; i++){
		cin >> h[i];
		if(i > 1 && h[i] != h[i-1]){
			fe = 0;
		}
	}
	int ss = 0;
	for(int i = 1; i <= n;i++){
		cin >> w[i];
		ss += w[i];
	}
	if(fe){
		cout << mul(f(ss), f(h[1]));
		return 0;
	}
	int ans = 0;
	if(n <= 1000){
		for(int i = 1; i <= n; i++){
			int mn = h[i];
			dp[i] = mul(w[i], f(h[i]));
			dp[i] = add(dp[i], mul(f(w[i]-1), f(h[i])));
			int res =0 ;
			for(int j = i-1; j >= 1; j--){
				mn = min(mn, h[j]);
				res = add(res, mul(w[j],f(mn)));
			}
			dp[i] = add(dp[i], mul(res, w[i]));
			ans = add(ans, dp[i]);
		}
		KILL(ans);
	}
	else if(is_sorted(h+1, h+n+1)){
		for(int i = 1; i <= n; i++){
			dp[i] = mul(w[i], f(h[i]));
			dp[i] = add(dp[i], mul(f(w[i]-1), f(h[i])));
			ps[i] = add(mul(w[i], f(h[i])),ps[i-1]);
			int res =0;
			res = ps[i-1];
			dp[i] = add(dp[i], mul(res, w[i]));
			ans = add(ans, dp[i]);
		}
		KILL(ans);
	}
}

• Subtask 1: 0 / 0
• Subtask 2: 12 / 12
• Subtask 3: 0 / 13
• Subtask 4: 15 / 15
• Subtask 5: 15 / 15
• Subtask 6: 18 / 18
• Subtask 7: 0 / 27