Submission #23343

#	Time	Username	Problem	Language	Result	Execution time	Memory
23343		duongthoi1999	Boat (APIO16_boat)	C++14	100 / 100	1076 ms	10088 KiB

boat

#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef long long ll;
typedef long double ld;
typedef pair<ll, int> ii;
const int mod = (int) 1e9 + 7;
const ll inf = 1LL << 60;
const int maxn = (int) 1005;
const ld eps = 1e-9;

void add(int &a, ll b) {
    a += (b % mod);
    while (a >= mod) a -= mod;
}

ll pw(ll a, int b) {
    ll res = 1;
    while (b) {
        if(b & 1) res = res * a % mod;
        a = a * a % mod;
        b >>= 1;
    }
    return res;
}

int n, m, a[maxn], b[maxn], sz[maxn];
int f[maxn][maxn], inv[maxn], C[maxn][maxn];
vector<int> p;

int main() {
    //freopen("test.txt", "r", stdin);
    ios_base::sync_with_stdio(0); cin.tie(0);
    cin >> n;
    rep(i, 1, n + 1) {
        cin >> a[i] >> b[i];
        b[i] ++;
        p.pb(a[i]);
        p.pb(b[i]);
        inv[i] = pw(i, mod - 2);
    }
    p.pb(0);
    sort(all(p));
    p.resize(unique(all(p)) - p.begin());
    rep(i, 1, n + 1) a[i] = lower_bound(all(p), a[i]) - p.begin();
    rep(i, 1, n + 1) b[i] = lower_bound(all(p), b[i]) - p.begin();
    m = SZ(p) - 2;
    rep(i, 1, m + 1) sz[i] = p[i + 1] - p[i];
    rep(i, 0, m + 1) f[0][i] = 1;
    rep(i, 1, n + 1) {
        rep(k, a[i], b[i]) {
            ll cnt = 1, x = sz[k], y = 1;
            per(j, 0, i) {
                if(a[j + 1] <= k && k < b[j + 1]) {
                    cnt = ((cnt * x % mod) * inv[y]) % mod;
                    x ++, y ++;
                }
                add(f[i][k], cnt * f[j][k - 1]);
            }
        }
        rep(j, 1, m + 1) add(f[i][j], f[i][j - 1]);
    }
    int ans = 0;
    rep(i, 1, n + 1) add(ans, f[i][m]);
    cout << ans << endl;
}

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