Submission #1086440

#	Time	Username	Problem	Language	Result	Execution time	Memory
1086440		anhthi	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	15 ms	14172 KiB

kangaroo

#include <bits/stdc++.h>

using namespace std;

#define fi first
#define se second
#define ll long long
#define mp(x, y) make_pair(x, y)
#define sz(v) ((int) (v).size())
#define all(v) (v).begin(), (v).end()
#define MASK(i) (1LL << (i))
#define BIT(x, y) (((x) >> (y)) & 1)
#define pb push_back
#define max_rng *max_element
#define min_rng *min_element
#define rep(i, n) for(int i = 1, _n = (n); i <= _n; ++i)
#define forn(i, a, b) for(int i = (a), _b = (b); i <= _b; ++i)
#define ford(i, a, b) for(int i = (a), _b = (b); i >= _b; --i)

template <class X, class Y>
    inline bool maximize(X &x, Y y) {
        return (x < y ? x = y, true : false);
    }

template <class X, class Y>
    inline bool minimize(X &x, Y y) {
        return (x > y ? x = y, true : false);
    }

template <class X>
    inline void compress(vector<X> &a) {
        sort(all(a));
        a.resize(unique(all(a)) - a.begin());
    }

int ctz(ll x) { return __builtin_ctzll(x); }
int lg(ll x) { return 63 - __builtin_clzll(x); }
int popcount(ll x) { return __builtin_popcount(x); }


mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rand(ll l, ll r) {
    return l + abs((ll) rng()) % (r - l + 1);
}

const ll oo = (ll) 1e17;
const int inf = (ll) 2e9 + 7, mod = (ll) 1e9 + 7;

const int mxn = 2e3 + 5, mxm = 1e3;
const int LG = 18, BASE = 311;

void sub(int &x, int y) { x -= y; if (x < 0) x += mod; }
void add(int &x, int y) { x += y; if (x >= mod) x -= mod; }

int n, cs, cf;
int f[mxn][mxn];

int main(void) {

    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    #define TASK "task"
    if (fopen(TASK".inp", "r")) {
        freopen(TASK".inp", "r", stdin);
        freopen(TASK".out", "w", stdout);
    }

    cin >> n >> cs >> cf;

    if (n == 2) return cout << 1, 0;

    f[1][1] = 1;
    forn(i, 1, n-1) forn(cc, 1, n) if (f[i][cc]) {
        if (i+1 == cs || i+1 == cf) {
            //create
            add(f[i+1][cc+1], f[i][cc]);
            // appends
            add(f[i+1][cc], f[i][cc]);
        }
        else {
            // merge
            add(f[i+1][cc-1], 1LL * (cc - 1) * f[i][cc] % mod);
            // create
            add(f[i+1][cc+1], 1LL * (cc + 1 - (cf < i + 1) - (cs < i + 1)) * f[i][cc] % mod);
        }
    }

    cout << f[n][1];

    return 0;
}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:65:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |         freopen(TASK".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:66:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   66 |         freopen(TASK".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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