Submission #493880

#	Time	Username	Problem	Language	Result	Execution time	Memory
493880		KhoaHo	Boat (APIO16_boat)	C++11	9 / 100	50 ms	1356 KiB

boat

/// KoJa
#include <bits/stdc++.h>
using namespace std;
#define task "DUT03TEAMS"
#define pb push_back
#define SZ(a) (a).begin(), (a).end()
#define SZZ(a, Begin, End) (a) + (Begin), (a) + (Begin) + (End)
#define BIT(a) (1LL << (a))
#define vec vector
#define fi first
#define se second

typedef long long ll;
typedef pair<int, int> ii;

template <class T>
inline bool maximize(T &a, const T &b) { return (a < b ? (a = b) : 0); }
template <class T>
inline bool minimize(T &a, const T &b) { return (a > b ? (a = b) : 0); }
void init()
{
    freopen(task ".inp", "r", stdin);
    freopen(task ".out", "w", stdout);
}
void fastio()
{
    ios_base::sync_with_stdio(NULL);
    cin.tie(NULL);
    cout.tie(NULL);
}
const int N = 505;
const int mod = int(1e9) + 7;
void add(int &a, const int &b)
{
    a += b;
    if (a >= mod)
        a -= mod;
}
const ll INF = 1e18;
int n, mem1[N][N];
ii a[N];

int backtrack1(int i, int x)
{
    if (i == n + 1)
    {
        if (x != -1)
            return 1;
        return 0;
    }
    int &res = mem1[i][x];
    if (res != -1)
        return res;
    res = 0;
    add(res, backtrack1(i + 1, x));
    if (a[i].fi > x)
        add(res, backtrack1(i + 1, a[i].fi));
    return res;
}
int res = 0, dp[N][N], pref[N + 10], fact[N], ifact[N];
int Pow(int x, int y)
{
    int res = 1;
    while (y)
    {
        if (y & 1)
            res = 1LL * res * x % mod;

        x %= mod;
        x = 1LL * x * x % mod;
        y /= 2;
    }
    return res;
}
int main()
{
    fastio();
    //init();
    cin >> n;
    bool sub1 = (n <= 500);
    for (int i = 1; i <= n; i++)
    {
        cin >> a[i].fi >> a[i].se;
        sub1 &= (a[i].fi == a[i].se);
    }
    fact[0] = 1;
    for (int i = 1; i < N; i++)
        fact[i] = 1LL * fact[i - 1] * i % mod;
    ifact[N - 1] = Pow(fact[N - 1], mod - 2);
    for (int i = N - 1; i >= 1; i--)
        ifact[i - 1] = 1LL * ifact[i] * i % mod;
    vec<int> val;
    if (sub1)
    {
        for (int i = 1; i <= n; i++)
            val.pb(a[i].fi);
        sort(SZ(val));
        val.erase(unique(SZ(val)), val.end());
        for (int i = 1; i <= n; i++)
            a[i].fi = lower_bound(SZ(val), a[i].fi) - val.begin() + 1;
        memset(mem1, -1, sizeof(mem1));
        return cout << backtrack1(1, -1), 0;
    }
    for (int i = 1; i <= n; i++)
    {
        val.pb(a[i].fi);
        val.pb(a[i].se + 1);
    }
    sort(SZ(val));
    val.erase(unique(SZ(val)), val.end());
    for (int i = 1; i <= n; i++)
        a[i] = ii(lower_bound(SZ(val), a[i].fi) - val.begin() + 1, lower_bound(SZ(val), a[i].se) - val.begin() + 1);
    for (int i = 0; i < N; i++)
        pref[i] = 1;
    dp[0][0] = 1;
    for (int i = 1; i <= n; i++)
    {
        for (int j = a[i].fi; j < a[i].se; j++)
        {
            int len = val[j + 1] - val[j];
            for (int k = N - 1; k >= 2; k--)
                add(dp[j][k], 1LL * dp[j][k - 1] * (len - k + 1) % mod * ifact[k] % mod);
            add(dp[j][1], 1LL * pref[j - 1] * len % mod);
        }
        pref[0] = dp[0][0];
        for (int j = 1; j < N; j++)
        {
            pref[j] = pref[j - 1];
            for (int k = 0; k < N; k++)
                add(pref[j], dp[j][k]);
        }
    }
    cout << (pref[N - 1] + mod - 1) % mod;
    return 0;
}

Compilation message (stderr)

boat.cpp: In function 'void init()':
boat.cpp:22:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   22 |     freopen(task ".inp", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
boat.cpp:23:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   23 |     freopen(task ".out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 0 / 22
• Subtask 3: 0 / 27
• Subtask 4: 0 / 42