Submission #1085996

#	Time	Username	Problem	Language	Result	Execution time	Memory
1085996		Spy007	Boat (APIO16_boat)	C++17	100 / 100	265 ms	10372 KiB

boat

#define Name Spy007
#include <bits/stdc++.h>
#define task "DL"
#define FOR(i,a,b) for (int i=(a),_b=(b);i<=_b;++i)
#define FOD(i,a,b) for (int i=(a),_b=(b);i>=_b;--i)
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define All(x) x.begin(),x.end()
#define sz(x) (int)x.size()
#define fast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define ll long long
#define endl '\n'
#define PI 3.14159265

using namespace std;

typedef pair <int,int> ii;
typedef pair <int,ii> iii;
typedef pair <int,ll> ill;
typedef pair <ll,ll> lll;
typedef vector <int> vi;
typedef vector <ii> vii;
typedef vector <vi> vvi;

const int nmax = 500;
const ll mod = 1e9 + 7;

int n, m;
ll inv[nmax + 5], g[2 * nmax + 5][nmax + 5], c[nmax + 5][nmax + 5], dp[nmax + 5][2 * nmax + 5];
ii a[nmax + 5];
vi val;

ll Pow(ll a, ll b)
{
    if (b == 1) return a % mod;
    ll tmp = Pow(a, b / 2);
    tmp = (tmp * tmp) % mod;
    if (b & 1) return (tmp * a) % mod;
    else return tmp;
}

vi Treat(vi val)
{
    sort(All(val));
    vi ans;
    ans.pb(val[0]);
    FOR(i, 1, sz(val) - 1)
    if (val[i] != val[i - 1]) ans.pb(val[i]);
    return ans;
}

void Prep(void)
{
    val = Treat(val);
    FOR(i, 1, n) inv[i] = Pow(i, mod - 2);
    FOR(i, 1, n)
    {
        c[i][0] = 1;
        FOR(j, 1, i)
        c[i][j] = (c[i - 1][j - 1] + c[i - 1][j]) % mod;
    }
    m = sz(val);
    FOR(i, 1, m - 1)
    {
        int len = val[i] - val[i - 1];
        g[i][0] = 1;
        FOR(j, 1, n)
        g[i][j] = (g[i][j - 1] * (((j + len - 1) * inv[j]) % mod)) % mod;
    }
}

void Input(void)
{
    cin >> n;
    FOR(i, 1, n)
    {
        cin >> a[i].fi >> a[i].se;
        val.pb(a[i].fi - 1);
        val.pb(a[i].se);
    }
}

void Solve(void)
{
    Prep();
    ll res = 0;
    FOR(i, 0, m - 1) dp[0][i] = 1;
    FOR(i, 1, n)
    {
        FOR(j, 1, m - 1)
        {
            if (a[i].fi <= val[j - 1] + 1 && val[j] <= a[i].se)
            {
                int cnt = 0;
                FOD(k, i, 1)
                {
                    if (a[k].fi <= val[j - 1] + 1 && val[j] <= a[k].se) cnt++;
                    dp[i][j] = (dp[i][j] + dp[k - 1][j - 1] * g[j][cnt]) % mod;
                }
                res = (res + dp[i][j]) % mod;
            }
            dp[i][j] = (dp[i][j] + dp[i][j - 1]) % mod;
        }
    }
    cout << res << endl;
}

signed main()
{
    fast;
    if (fopen(task".inp","r"))
    {
        freopen(task".inp","r",stdin);
        freopen(task".out","w",stdout);
    }
    Input();
    Solve();
    return 0;
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:115:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  115 |         freopen(task".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
boat.cpp:116:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  116 |         freopen(task".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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