Submission #249908

#	Time	Username	Problem	Language	Result	Execution time	Memory
249908		receed	Boat (APIO16_boat)	C++14	100 / 100	600 ms	30972 KiB

boat

#include <iostream>
#include <iomanip>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstring>
#include <cassert>
#include <string>
#include <set>
#include <map>
#include <random>
#include <bitset>
#include <string>
#include <unordered_set>
#include <unordered_map>
#include <deque>
#include <queue>
#define rep(i, n) for (int i = 0; i < (n); i++)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()

using namespace std;
using ll = long long;
using ul = unsigned long long;
using ld = long double;

const int N = 1001;
const ll MOD = 1e9 + 7, M2 = MOD * MOD;
ll a[N], b[N], ps[N][N], c[N][N], cd[N][N], rev[N], cs[N][N], dp[N][N];

ll pw(ll x, ll k) {
    ll r = 1;
    while (k) {
        if (k & 1)
            r = r * x % MOD;
        k >>= 1;
        x = x * x % MOD;
    }
    return r;
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    ll n, d;
    cin >> n;
    vector<ll> li;
    rep(i, n) {
        cin >> a[i] >> b[i];
        b[i]++;
        li.push_back(a[i]);
        li.push_back(b[i]);
    }
    sort(all(li));
    li.resize(unique(all(li)) - li.begin());
    int m = li.size();
    rep(i, n) {
        a[i] = lower_bound(all(li), a[i]) - li.begin();
        b[i] = lower_bound(all(li), b[i]) - li.begin();
        rep(j, m)
            ps[j][i + 1] = ps[j][i] + (a[i] <= j && j < b[i]);
    }
    rep(i, n + 1) {
        c[i][0] = 1;
        for (int j = 1; j <= i; j++)
            c[i][j] = (c[i - 1][j - 1] + c[i - 1][j]) % MOD;
        rev[i] = pw(i, MOD - 2);
    }
    rep(i, m - 1) {
        d = li[i + 1] - li[i];
        cd[i][1] = d;
        for (int j = 1; j < n; j++)
            cd[i][j + 1] = cd[i][j] * (d - j) % MOD * rev[j + 1] % MOD;
        for (int j = 1; j <= n; j++) {
            for (int k = 1; k <= j; k++) {
                cs[i][j] += c[j - 1][k - 1] * cd[i][k];
                if (cs[i][j] >= M2)
                    cs[i][j] -= M2;
            }
            cs[i][j] %= MOD;
        }
    }
    rep(i, n) {
        for (int j = a[i]; j < b[i]; j++) {
            dp[i + 1][j] = cs[j][ps[j][i + 1]];
            if (j)
                rep(k, i + 1) {
                    dp[i + 1][j] += dp[k][j - 1] * cs[j][ps[j][i + 1] - ps[j][k]];
                    if (dp[i + 1][j] >= M2)
                        dp[i + 1][j] -= M2;
                }
            dp[i + 1][j] %= MOD;
        }
        rep(j, m)
            dp[i + 1][j + 1] = (dp[i + 1][j] + dp[i + 1][j + 1]) % MOD;
    }
    ll ans = 0;
    rep(i, n + 1) {
        ans = (ans + dp[i][m]) % MOD;
    }
    cout << ans;
}

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