Submission #633977

#	Time	Username	Problem	Language	Result	Execution time	Memory
633977		Denisov	Kangaroo (CEOI16_kangaroo)	C++14	0 / 100	0 ms	212 KiB

kangaroo

#include <bits/stdc++.h>
#include <ext/rope>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
//#define int long long
#define pb push_back
#define x first
#define y second
#define mk(a,b) make_pair(a,b)
#define rr return 0
#define sqr(a) ((a)*(a))
#define all(a) (a).begin(), (a).end()
#define sz(a) (int)(a).size()
#undef M_PI
#define M_PI 3.14159265358979323846264338327950288419

using namespace std;
using namespace __gnu_cxx;
using namespace __gnu_pbds;

using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using big = __int128;

template<class value, class cmp = less<value> >
using ordered_set = tree<value, null_type, cmp, rb_tree_tag, tree_order_statistics_node_update>;
template<class value, class cmp = less_equal<value> >
using ordered_multiset = tree<value, null_type, cmp, rb_tree_tag, tree_order_statistics_node_update>;
template<class key, class value, class cmp = less<key> >
using ordered_map = tree<key, value, cmp, rb_tree_tag, tree_order_statistics_node_update>;

/// find_by_order()
/// order_of_key()
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
template<typename T = int>
inline T randll(T l = INT_MIN, T r = INT_MAX) {
    return uniform_int_distribution<T>(l, r)(rng);
}

inline ld randld(ld l = INT_MIN, ld r = INT_MAX) {
    return uniform_real_distribution<ld>(l, r)(rng);
}

const int INF = 2e9 + 11;
const int MOD = 1e9 + 7; /// think
const ll LINF = ll(2e18) + 11;

const int dx[] = {0, 0, 1, -1}, dy[] = {1, -1, 0, 0};

template<class T> bool umin (T &a, T b) {return a > b ? (a = b, true) : false; }
template<class T> bool umax (T &a, T b) {return a < b ? (a = b, true) : false; }


#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif


struct mint {
    int val;

    mint () : val(0) {}
    mint (int x) {
        if (-MOD <= x && x < MOD) {
            val = x;
        }
        else {
            val = x % MOD;
        }
        if (val < 0) val += MOD;
    }

    mint (ll x) {
        if (-MOD <= x && x < MOD) {
            val = x;
        }
        else {
            val = x % MOD;
        }
        if (val < 0) val += MOD;
    }

    mint (const mint& x) : val(x.val) {}

    constexpr mint& operator = (const mint& x) {
        val = x.val;
        return *this;
    }

    inline mint& operator += (const mint &x) {
        val += x.val;
        if (val >= MOD) {
            val -= MOD;
        }
        return *this;
    }

    inline mint& operator -= (const mint &x) {
        val -= x.val;
        if (val < 0) {
            val += MOD;
        }
        return *this;
    }

    inline mint operator - () const {
        mint tmp(*this);
        if (tmp.val) tmp.val = MOD - tmp.val;
        return tmp;
    }

    inline mint operator + (const mint &x) const {
        return mint(*this) += x;
    }

    inline mint operator - (const mint &x) const {
        return mint(*this) -= x;
    }

    inline mint& operator *= (const mint &x) {
        val = ((ll)val * x.val) % MOD;
        return *this;
    }

    inline mint operator * (const mint &x) const {
        return mint(*this) *= x;
    }

    inline mint binpow (int n) const {
        mint res = 1, tmp = *this;
        for (; n; n >>= 1) {
            if (n & 1) {
                res *= tmp;
            }
            tmp *= tmp;
        }
        return res;
    }

    inline mint inverse () const {
        return binpow(MOD - 2);
    }

    inline mint& operator /= (const mint &x) {
        return *this *= x.inverse();
    }

    inline mint operator / (const mint &x) {
        return mint(*this) *= x.inverse();
    }


    friend ostream& operator << (ostream &os, const mint &x) {
        os << x.val;
        return os;
    }

    friend istream& operator >> (istream &is, mint &x) {
        is >> x.val;
        return is;
    }

    inline bool operator == (const mint &x) const {
        return val == x.val;
    }

    inline bool operator != (const mint &x) const {
        return val != x.val;
    }

    inline bool operator < (const mint &x) const {
        return val < x.val;
    }

    inline bool operator > (const mint &x) const {
        return val > x.val;
    }

    friend string to_string (const mint &x) {
        return to_string(x.val);
    }

};

vector <mint> f = {1}, fi = {1};

inline mint fact (int n) {
    f.reserve(n + 1);
    while (sz(f) <= n) {
        f.emplace_back(f.back() * sz(f));
    }
    return f[n];
}

inline mint inv_fact (int n) { /// think
    if (sz(fi) <= n) {
        fi.resize(n + 1, 0);
        mint val = mint(1) / fact(n);
        for (int i = n; fi[i] == 0; i--) {
            fi[i] = val;
            val *= i;
        }
    }
    return fi[n];
}

inline mint A (int n, int k) {
    if (k < 0 || k > n) return 0;
    return fact(n) * inv_fact(n - k);
}

inline mint C (int n, int k) {
    if (k < 0 || k > n) return 0;
    return A(n, k) * inv_fact(k);
}

inline void test_case () {
    int n, a, b;
    cin >> n >> a >> b;
    vector <vector <mint> > dp(n + 1, vector <mint> (n + 1));
    dp[1][1] = 1;
    for (int i = 1; i < n; i++) {
        for (int j = 0; j <= i; j++) {
            if (i + 1 == a || i + 1 == b) {
                dp[i + 1][j] += dp[i][j];
                if (j + 1 <= n) {
                    dp[i + 1][j + 1] += dp[i][j];
                }
            }
            else {
                if (j + 1 <= n) {
                    dp[i + 1][j + 1] += dp[i][j] * (j + 1 - (i + 1 < a) - (i + 1 < b));
                }
                if (j - 1 >= 0) {
                    dp[i + 1][j - 1] += dp[i][j] * (j - 1);
                }
            }
        }
    }
    cout << dp[n][1] << '\n';
}


main()
{
    ios::sync_with_stdio(0);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t = 1;
//    cin >> t;
    for (int test = 1; test <= t; test++) {
        test_case();
    }
}

Compilation message (stderr)

kangaroo.cpp:252:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
  252 | main()
      | ^~~~

• Subtask 1: 0 / 6
• Subtask 2: 0 / 30
• Subtask 3: 0 / 15
• Subtask 4: 0 / 49