Submission #1132893

#	Time	Username	Problem	Language	Result	Execution time	Memory
1132893		turska	Flooding Wall (BOI24_wall)	C++20	36 / 100	446 ms	314692 KiB

Main

// #pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;
template <class T>
using indexed_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
/*using ll = __int128;*/
using ll = long long;
using ull = unsigned long long;

using pii = pair<int, int>;
using pll = pair<ll, ll>;

/*const ll M = 998244353;*/
const ll M = 1e9 + 7;

#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define ff first
#define ss second
#define PI 3.141592653589793238462643383279502884L

const ll INFL = 1e18;
const int INF = 1e9;
const int maxN = 101+1;


ll suf[10002][1002], suf_sum[10002][1002];
ll pref[10002][1002], pref_sum[10002][1002];
ll a[10001], b[10001];
void solve() {
    int n;
    cin >> n;
    for (int i=1; i<=n; i++) cin >> a[i];
    for (int i=1; i<=n; i++) cin >> b[i];

    pref[0][0] = 1;
    for (int i=1; i<=n; i++) {
        for (auto v: {a[i], b[i]}) {
            for (int j=v+1; j<=1000; j++) {
                pref[i][j] += pref[i-1][j];
                pref[i][j] %= M;
            }
            for (int j=0; j<=v; j++) {
                pref[i][v] += pref[i-1][j];
                pref[i][j] %= M;
            }
        }
        for (int j=1000; j>=0; j--) {
            pref_sum[i][j] = pref_sum[i][j+1] + pref[i][j];
            pref_sum[i][j] %= M;
        }
    }
    suf[n+1][0] = 1;
    for (int i=n; i>=1; i--) {
        for (auto v: {a[i], b[i]}) {
            for (int j=v+1; j<=1000; j++) {
                suf[i][j] += suf[i+1][j];
                suf[i][j] %= M;
            }
            for (int j=0; j<=v; j++) {
                suf[i][v] += suf[i+1][j];
                suf[i][j] %= M;
            }
        }
        for (int j=1000; j>=0; j--) {
            suf_sum[i][j] = suf_sum[i][j+1] + suf[i][j];
            suf_sum[i][j] %= M;
        }
    }
    ll ans = 0;
    for (int i=1; i<=n; i++) {
        for (auto v: {a[i], b[i]}) {
            for (int j=v+1; j<=1000; j++) {
                ans += pref[i-1][j]*suf_sum[i+1][j+1]%M*(j-v);
                ans += suf[i+1][j]*pref_sum[i-1][j+1]%M*(j-v);
                ans += pref[i-1][j]*suf[i+1][j]%M*(j-v);
                ans %= M;
            }
        }
    }
    cout << ans << '\n';
};


int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
    cout << fixed << setprecision(12);
    int tc = 1;
    /*cin >> tc;*/
    while (tc--) solve();
}

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