Submission #1027936

#	Time	Username	Problem	Language	Result	Execution time	Memory
1027936		Issa	Flooding Wall (BOI24_wall)	C++17	70 / 100	3734 ms	1048576 KiB

Main

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define ent "\n"

const int maxn = 1e6 + 100;
const ll INF = (ll)1e18 + 100;
const int inf = 1e9 + 100;
const int MOD = 1e9 + 7;
const int maxl = 26;
const int P = 31;

int n;
int a[maxn][2];
vector<int> dp[maxn];

void upd(int &x, int y){
	x = (x + y) % MOD;
}

void test(){
	cin >> n;
	vector<int> s = {-1};
	for(int i = 1; i <= n; i++){
		cin >> a[i][0];
	}
	for(int i = 1; i <= n; i++){
		cin >> a[i][1];
		s.push_back(a[i][0]);
		s.push_back(a[i][1]);
	}
	sort(s.begin(), s.end());
	s.resize(unique(s.begin(), s.end()) - s.begin());
	for(int i = 1; i <= n; i++){
		a[i][0] = lower_bound(s.begin(), s.end(), a[i][0]) - s.begin();
		a[i][1] = lower_bound(s.begin(), s.end(), a[i][1]) - s.begin();
		if(a[i][0] > a[i][1]) swap(a[i][0], a[i][1]);
	}
	dp[0] = vector<int>(s.size(), 0);
	dp[0][0] = 1;
	for(int i = 1; i <= n; i++){
		dp[i] = dp[i-1];
		for(int j = s.size()-1; j >= 0; j--){
			ll x = dp[i][j];
			dp[i][j] = 0;
			upd(dp[i][max(j, a[i][1])], x);
			upd(dp[i][max(j, a[i][0])], x);
		}
	}
	vector<int> d = vector<int>(s.size(), 0);
	d[0] = 1; ll ans = 0;
	for(int i = n; i > 0; i--){
		ll sum1 = 0, sum2 = 0;
		for(int j = s.size() - 1; j >= 0; j--){
			sum1 = (sum1 + dp[i-1][j]) % MOD;
			ll cnt = (1ll * d[j] * sum1 + dp[i-1][j] * sum2) % MOD;
			sum2 = (sum2 + d[j]) % MOD;
			if(j > a[i][1]){
				ans = (ans + 1ll * (s[j] - s[a[i][1]]) * cnt) % MOD;
			} if(j > a[i][0]){
				ans = (ans + 1ll * (s[j] - s[a[i][0]]) * cnt) % MOD;
			}
		}
		for(int j = s.size()-1; j >= 0; j--){
			ll x = d[j];
			d[j] = 0;
			upd(d[max(j, a[i][1])], x);
			upd(d[max(j, a[i][0])], x);
		}
	}
	cout << ans;
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    int t; t = 1;
    while(t--) test();
    cout << ent;
}

• Subtask 1: 8 / 8
• Subtask 2: 17 / 17
• Subtask 3: 19 / 19
• Subtask 4: 14 / 14
• Subtask 5: 12 / 12
• Subtask 6: 0 / 30