Submission #1078378

#	Time	Username	Problem	Language	Result	Execution time	Memory
1078378		underwaterkillerwhale	Boat (APIO16_boat)	C++17	100 / 100	631 ms	7508 KiB

boat

#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) (ll)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 = 5e2 + 7;
const int Mod = 1e9 + 7;
const int INF = 1e9;
const ll BASE = 137;
const int szBL = 320;

int n, m;
pii a[N];
int dp[N][N * 2], f[N][N * 2], com[N * 2][N], combi[N][N];

inline void add (int &a, int b) { a = a + b; if (a >= Mod) a = a - Mod; }

ll power (int n, int m) {
    if (m == 0) return 1;
    ll t = power (n, m >> 1);
    (t *= t) %= Mod;
    if (m & 1) (t *= n) %= Mod;
    return t;
}

bool cover (pii A, pii B) {
    return A.fs <= B.fs && A.se >= B.se;
}

void solution () {
    cin >> n;
    vector<pii> vec, seg = {MP(0, 0)};
    rep (i, 1, n) {
        cin >> a[i].fs >> a[i].se;
        vec.pb({a[i].fs, 0}), vec.pb({a[i].se, 1});
    }
    sort (ALL(vec));
    vec.resize(unique(ALL(vec)) - vec.begin());
    rep (i, 0, SZ(vec) - 2) {
        if (vec[i].se == vec[i + 1].se) {
            if (vec[i].se == 1) seg.pb({vec[i].fs + 1, vec[i + 1].fs});
            else seg.pb({vec[i].fs, vec[i + 1].fs - 1});
        }
        else {
            if (vec[i].se == 0) seg.pb({vec[i].fs, vec[i + 1].fs});
            else seg.pb({vec[i].fs + 1, vec[i +1 ].fs - 1});
        }
    }
    m = SZ(seg) - 1;
    rep (i, 0, m) {
        int Len = seg[i].se - seg[i].fs + 1;
        com[i][0] = 1;
        rep (j, 1, n + 1) {
            if (j > Len) com[i][j] = 0;
            else com[i][j] = 1LL * com[i][j - 1] * (Len - j + 1) % Mod * power (j, Mod - 2) % Mod;
        }
//        cout << seg[i].fs <<","<<seg[i].se<<"\n";
    }
    rep (i, 0, n) {
        rep (j, 0, i) {
            if (j == i || j == 0) combi[i][j] = 1;
            else combi[i][j] = (combi[i - 1][j - 1] + combi[i - 1][j]) % Mod;
        }
    }
    rep (i, 0, n) {
        rep (j, 0, m) {
            rep (k, 0, i) {
                add(f[i][j], 1LL * combi[i][k] * com[j][k + 1] % Mod);
            }
        }
    }
    rep (j, 0, m) dp[0][j] = 1;
    rep (i, 1, n) {
        dp[i][0] = 1;
        rep (j, 1, m) {
            dp[i][j] = dp[i][j - 1];
            int num = 0;
            reb (k, i, 1) {
                if (cover(a[k], seg[j])) {
                    add(dp[i][j], 1LL * dp[k - 1][j - 1] * f[num][j] % Mod);
                    ++num;
                }
            }
//            cout << i <<" "<<seg[j].fs<<","<<seg[j].se<<": "<<dp[i][j] <<"\n";
        }
    }
    cout << (dp[n][m] - 1 + Mod) % Mod <<"\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?
4 5
1 3
4 1
1 2
3 2
2 1
return->break
*/

• Subtask 1: 9 / 9
• Subtask 2: 22 / 22
• Subtask 3: 27 / 27
• Subtask 4: 42 / 42