Submission #1069588

#	Time	Username	Problem	Language	Result	Execution time	Memory
1069588		underwaterkillerwhale	Flooding Wall (BOI24_wall)	C++17	17 / 100	5088 ms	187692 KiB

Main

#include <bits/stdc++.h>
#define ll long long
#define rep(i,m,n) for(int i=(m); i<=(n); i++)
#define reb(i,m,n) for(int i=(m); i>=(n); i--)
#define pii pair<int,int>
#define pll pair<ll,ll>
#define MP make_pair
#define fs first
#define se second
#define bit(msk, i) ((msk >> i) & 1)
#define iter(id, v) for(auto id : v)
#define pb push_back
#define SZ(v) (int)v.size()
#define ALL(v) v.begin(),v.end()

using namespace std;

mt19937_64 rd(chrono :: steady_clock :: now ().time_since_epoch().count());
ll Rand (ll l, ll r) { return uniform_int_distribution<ll> (l, r) (rd); }

const int N = 1e4 + 2;
const int Mod = 1e9 + 7;
const ll INF = 1e18 + 7;
const ll BASE = 137;
const int szBL = 320;

int n, m;
int a[2][N];
ll dp[N][N], f[N][N];

void solution () {
    cin >> n;
    rep (i, 1, n) cin >> a[0][i];
    rep (i, 1, n) {
        cin >> a[1][i];
        if (a[1][i] <= a[0][i]) swap(a[1][i], a[0][i]);
    }
    m = *max_element(a[1] + 1, a[1] + 1 + n);
    dp[1][a[1][1]] = 1;
    dp[1][a[0][1]] = 1;
    rep (i, 2, n) {
        rep (k, 0, 1) {
            rep (j, 1, m) {
                if (j <= a[k][i]) {
                    (dp[i][a[k][i]] += dp[i - 1][j]) %= Mod;
                }
                else {
                    (dp[i][j] += dp[i - 1][j]) %= Mod;
                }
            }
//            rep (j, 1, m)
//                cout << i <<" "<<j<<" "<<dp[i][j] <<"\n";
        }
    }
//    cout<<"\n";
    f[n][a[0][n]] = 1;
    f[n][a[1][n]] = 1;

    reb (i, n - 1, 1)
    rep (k, 0, 1) {
        rep (j, 1, m) {
            if (j <= a[k][i]) {
                (f[i][a[k][i]] += f[i + 1][j]) %= Mod;
            }
            else {
                (f[i][j] += f[i + 1][j])%= Mod;
            }
        }
//        rep (j, 1, m)
//                cout << i <<" "<<j<<" "<<f[i][j] <<"\n";
    }
    ll res  = 0;
    rep (i, 1, n) {
        rep (k, 0, 1) {
//            cout << i<<" "<<a[k][i] <<"\n";
            rep (j, a[k][i] + 1, m)
            rep (p, a[k][i] + 1, m) {
                (res += dp[i - 1][j] * f[i + 1][p] % Mod * (min(j, p) - a[k][i]) % Mod) %= Mod;
//                cout << i<<" "<<j<<" "<<p<<" "<<dp[i - 1][j] * f[i + 1][p] <<" a\n";
            }
        }
    }
    cout << res<<"\n";

}

#define file(name) freopen(name".inp","r",stdin); \
freopen(name".out","w",stdout);
int main () {
//    file("c");
    ios_base :: sync_with_stdio(false); cin.tie(0); cout.tie(0);
    int num_Test = 1;
//    cin >> num_Test;
    while (num_Test--)
        solution();
}
/*
no bug challenge +4
mình có muốn dùng mảng này không?
2 + 8 * 2 - 9
4
1 1 1 1
2 2 2 2
*/

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