Submission #954930

#	Time	Username	Problem	Language	Result	Execution time	Memory
954930		Hando	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	63 ms	31860 KiB

kangaroo

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

#define ar array
#define vt vector
#define pq priority_queue
#define pu push
#define pub push_back
#define em emplace
#define emb emplace_back
#define mt make_tuple

#define all(x) x.begin(), x.end()
#define allr(x) x.rbegin(), x.rend()
#define allp(x, l, r) x.begin() + l, x.begin() + r
#define len(x) (int)x.size()
#define uniq(x) unique(all(x)), x.end()

using ll = long long;
using ld = long double;
using ull = unsigned long long;

template<class Fun> class y_combinator_result {
    Fun fun_;
public:
    template<class T> explicit y_combinator_result(T &&fun): fun_(std::forward<T>(fun)) {}
    template<class ...Args> decltype(auto) operator()(Args &&...args) { return fun_(std::ref(*this), std::forward<Args>(args)...); }
};
template<class Fun> decltype(auto) y_combinator(Fun &&fun) { return y_combinator_result<std::decay_t<Fun>>(std::forward<Fun>(fun)); }

template <class T, size_t N>
void re(array <T, N>& x);
template <class T> 
void re(vt <T>& x);

template <class T> 
void re(T& x) {
    cin >> x;
}

template <class T, class... M> 
void re(T& x, M&... args) {
    re(x), re(args...);
}

template <class T> 
void re(vt <T>& x) {
    for(auto& it : x) re(it);
}

template <class T, size_t N>
void re(array <T, N>& x) {
    for(auto& it : x) re(it);
}

template <class T, size_t N>
void wr(const array <T, N>& x);
template <class T> 
void wr(const vt <T>& x);

template <class T> 
void wr(const T& x) {
    cout << x;
}

template <class T, class ...M>  
void wr(const T& x, const M&... args) {
    wr(x), wr(args...);
}

template <class T> 
void wr(const vt <T>& x) {
    for(auto it : x) wr(it, ' ');
}

template <class T, size_t N>
void wr(const array <T, N>& x) {
    for(auto it : x) wr(it, ' ');
}

template<class T, class... M>
auto mvt(size_t n, M&&... args) {
    if constexpr(sizeof...(args) == 1)
        return vector<T>(n, args...);
    else
        return vector(n, mvt<T>(args...));
}

void set_fixed(int p = 0) {
    cout << fixed << setprecision(p);
}

void set_scientific() {
    cout << scientific;
}

void Open(const string& name) {
#ifndef ONLINE_JUDGE
    (void)!freopen((name + ".in").c_str(), "r", stdin);
    (void)!freopen((name + ".out").c_str(), "w", stdout);
#endif
}

const int mod = 1e9 + 7;

template <const int MOD>
struct modint {
    ll x;
    modint(): x(0) {}
    modint(ll x): x((x % MOD + MOD) % MOD) {}

    inline modint <MOD>& fix() {
        x = (x % MOD + MOD) % MOD;
        return *this;
    }

    inline modint <MOD> operator + (modint<MOD> other) const { 
        ll c = x + other.x;
        return modint<MOD>(c);
    }

    inline modint <MOD> operator - (modint<MOD> other) const { 
        ll c = x - other.x; 
        return modint<MOD>(c); 
    }
    
    inline modint <MOD> operator * (modint<MOD> other) const { 
        ll c = (ll)x * other.x; 
        return modint<MOD>(c); 
    }

    inline modint <MOD>& operator += (modint<MOD> other) { 
        x += other.x;
        this-> fix();
        return *this; 
    }

    inline modint <MOD>& operator -= (modint<MOD> other) { 
        x -= other.x; 
        this-> fix();
        return *this; 
    }

    inline modint <MOD>& operator *= (modint<MOD> other) { 
        x = (x * other.x) % MOD;
        this-> fix(); 
        return *this; 
    }

    inline modint <MOD> operator - () const { 
        return modint<MOD>(-x); 
    }
    
    // (++x)
    inline modint<MOD>& operator++() {
        x = (x + 1);
        this-> fix();
        return *this;
    }

    // (x++)
    inline modint<MOD> operator++(int) {
        modint<MOD> tmp(*this);
        ++(*this);
        return tmp;
    }

    // (--x)
    inline modint<MOD>& operator--() {
        x = (x - 1);
        this-> fix();
        return *this;
    }

    // (x--)
    inline modint<MOD> operator--(int) {
        modint<MOD> tmp(*this);
        --(*this);
        return tmp;
    }

    explicit operator long long() const {
        return x;
    }


    ll inv(ll a, ll b) const {
        return 1 < a? b - inv(b % a, a) * b / a : 1;
    }

    modint<MOD> lgput(modint<MOD> a, ll b) const {
        modint<MOD> res = 1; 
        while (b) {
            if (b & 1)
                res = res * a;
            a = a * a;
            b >>= 1;
        }
        return res;
    }

    inline modint<MOD> operator^(ll b) {
        return lgput(*this, b);
    }

    inline modint<MOD> operator ~() const {
        return modint<MOD>(inv(this->x, MOD)); 
    }

    inline modint<MOD> operator / (modint<MOD> other) const { 
        return *this * (~other); 
    }

    inline modint<MOD>& operator /= (modint<MOD> other) { 
        return *this *= (~other); 
    }

    inline bool operator == (modint<MOD> other) const { 
        return x == other.x; 
    }

    inline bool operator != (modint<MOD> other) const { 
        return x != other.x; 
    }

    inline bool operator < (modint<MOD> other) const { 
        return x < other.x; 
    }

    inline bool operator > (modint<MOD> other) const { 
        return x > other.x; 
    }
};

template <const int MOD> modint<MOD> operator + (ll value, modint<MOD> n) { 
    return modint<MOD>(modint<MOD>(value) + n); 
}

template <const int MOD> modint<MOD> operator + (int value, modint<MOD> n) { 
    return modint<MOD>(modint<MOD>(value) + n); 
}

template <const int MOD> modint<MOD> operator - (ll value, modint<MOD> n) { 
    return modint<MOD>(modint<MOD>(value) - n); 
}

template <const int MOD> modint<MOD> operator - (int value, modint<MOD> n) { 
    return modint<MOD>(modint<MOD>(value) - n); 
}

template <const int MOD> modint<MOD> operator * (ll value, modint<MOD> n) { 
    return modint<MOD>(modint<MOD>(value) * n); 
}

template <const int MOD> modint<MOD> operator * (int value, modint<MOD> n) { 
    return modint<MOD>(modint<MOD>(value) * n); 
}

template <const int MOD> istream& operator >> (istream& in, modint<MOD> n) { 
    return in >> n.x;
}

template <const int MOD> ostream& operator << (ostream& out, modint<MOD> n) { 
    return out << n.x;
}

using mint = modint<mod>;

void solve() {
    int n, a, b; re(n, a, b);

    vt <vt <mint>> dp(n + 1, vt <mint>(n + 1));

    dp[1][1] = 1;
    for (int i = 2; i <= n; ++i) {
        for (int j = 1; j <= n; ++j) {
            if (i == a || i == b)
                dp[i][j] = dp[i - 1][j - 1] + dp[i - 1][j];
            else
                dp[i][j] = dp[i - 1][j + 1] * j + 
                           dp[i - 1][j - 1] * (j - (i >= a) - (i >= b));
        }
    }

    wr(dp[n][1], '\n');
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    //Open("");

    int t = 1;
    for(;t;t--) {
        solve();
    }
    
    return 0;
}

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